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Bioelectrocatalytic Conversion from N2 to Chiral Amino Acids in a H2/α-Keto Acid Enzymatic Fuel Cell
Enzymatic electrosynthesis is a promising approach to produce useful chemicals with the requirement of external electrical energy input. Enzymatic fuel cells (EFCs) are devices to convert chemical energy to electrical energy via the oxidation of fuel at the anode and usually the reduction of oxygen or peroxide at the cathode. The integration of enzymatic electrosynthesis with EFC architectures can simultaneously result in self-powered enzymatic electrosynthesis with more valuable usage of electrons to produce high-value-added chemicals. In this study, a H2/α-keto acid EFC was developed for the conversion from chemically inert nitrogen gas to chiral amino acids, powered by H2 oxidation. A highly efficient cathodic reaction cascade was first designed and constructed. Powered by an applied voltage, the cathode supplied enough reducing equivalents to support the NH3 production and NADH recycling catalyzed by nitrogenase and diaphorase. The produced NH3 and NADH were reacted in situ with leucine dehydrogenase (LeuDH) to generate l-norleucine with 2-ketohexanoic acid as the NH3 acceptor. A 92% NH3 conversion ratio and 87.1% Faradaic efficiency were achieved. On this basis, a H2-powered fuel cell with hyper-thermostable hydrogenase (SHI) as the anodic catalyst was combined with the cathodic reaction cascade to form the H2/α-keto acid EFC. After 10 h of reaction, the concentration of l-norleucine achieved 0.36 mM with >99% enantiomeric excess and 82% Faradaic efficiency. From the broad substrate scope and the high enzymatic enantioselectivity of LeuDH, the H2/α-keto acid EFC is an energy-efficient alternative to electrochemically produce chiral amino acids for biotechnology applications.
Cai, Rong,Chen, Hsiaonung,Chen, Hui,Dong, Fangyuan,Minteer, Shelley D.,Prater, Matthew B.
supporting information
p. 4028 - 4036
(2020/03/11)

Semi-rational hinge engineering: modulating the conformational transformation of glutamate dehydrogenase for enhanced reductive amination activity towards non-natural substrates
The active site is the common hotspot for rational and semi-rational enzyme activity engineering. However, the active site represents only a small portion of the whole enzyme. Identifying more hotspots other than the active site for enzyme activity engineering should aid in the development of biocatalysts with better catalytic performance. Glutamate dehydrogenases (GluDHs) are promising and environmentally benign biocatalysts for the synthesis of valuable chirall-amino acids by asymmetric reductive amination of α-keto acids. GluDHs contain an inter-domain hinge structure that facilitates dynamic reorientations of the domains relative to each other. Such hinge-bending conformational motions of GluDHs play an important role in regulating the catalytic activity. Thus, the hinge region represents a potential hotspot for catalytic activity engineering for GluDHs. Herein, we report semi-rational activity engineering of GluDHs with the hinge region as the hotspot. Mutants exhibiting significantly improved catalytic activity toward several non-natural substrates were identified and the highest activity increase reached 104-fold. Molecular dynamics simulations revealed that enhanced catalytic activity may arise from improving the open/closed conformational transformation efficiency of the protein with hinge engineering. In the batch production of three valuablel-amino acids, the mutants exhibited significantly improved catalytic efficiency, highlighting their industrial potential. Moreover, the catalytic activity of several active site tailored GluDHs was also increased by hinge engineering, indicating that hinge and active site engineering are compatible. The results show that the hinge region is a promising hotspot for activity engineering of GluDHs and provides a potent alternative for developing high-performance biocatalysts toward chirall-amino acid production.
Liu, Yayun,Meng, Lijun,Wu, Jianping,Yang, Lirong,Yin, Xinjian,Zhou, Haisheng
p. 3376 - 3386
(2020/06/09)

Combinatorial Mutation Analysis of ω-Transaminase to Create an Engineered Variant Capable of Asymmetric Amination of Isobutyrophenone
ω-Transaminase (ω-TA) is an important enzyme for asymmetric synthesis of chiral amines. Rapid creation of a desirable ω-TA variant, readily available for scalable process operation, is demanded and has attracted intense research efforts. In this study, we aimed to develop a quantitative mutational analysis (i. e., R-analysis) that enables prediction of combinatorial mutation outcomes and thereby provides reliable guidance of enzyme engineering through combination of already characterized mutations. To this end, we determined three mutatable active-site residues of ω-TA from Ochrobactrum anthropi (i. e., leucine 57, tryptophan 58 and valine 154) by examining activities of nine alanine-scanning mutants for seven substrate pairs. The R-analysis of the mutatable residues is based on assessment of changes in relative activities for a series of structurally analogous substrates. Using three sets of substrates (five α-keto acids, six arylalkylamines and three arylalkyl ketones), we found that combination of two point mutations display additive effects of each mutational outcome such as steric relaxation for bulky substrates or catalytic enhancement for amination of ketones. Consistent with the R-analysis-based prediction, the ω-TA variant harboring triple alanine mutations, i. e. L57A, W58A and V154A, showed high activity improvements for bulky substrates, e. g. a 3.2×104-fold activity increase for 1-phenylbutylamine. The triple mutant even enabled asymmetric amination of isobutyrophenone, carrying a branched-chain alkyl substituent to be accepted in a small binding pocket that normally shows a steric limit up to an ethyl group, with >99% ee of a resulting (S)-amine. (Figure presented.).
Kim, Hong-Gon,Han, Sang-Woo,Shin, Jong-Shik
p. 2594 - 2606
(2019/05/15)

Artificial Biocatalytic Cascade with Three Enzymes in One Pot for Asymmetric Synthesis of Chiral Unnatural Amino Acids
Two biocatalytic reactions, transamination catalyzed by transaminases and reductive amination catalyzed by amino acid dehydrogenases, can be used for asymmetric synthesis of optically pure unnatural amino acids. However, although transaminases show a great diversity and broad substrate spectrum, most transaminase reactions are reversible, while amino acid dehydrogenases catalyze reductive amination irreversibly but with strict substrate specificity. Accordingly, herein we developed a tri-enzyme one-pot reaction system to exploit the respective advantages of transaminases and amino acid dehydrogenases, while overcoming the disadvantages of each. In this work, representatives of all four subgroups of transaminases coupled with different amino acid dehydrogenases to produce five l- and four d- unnatural amino acid products, using ammonia and the co-enzyme NAD(P)H, which is regenerated by a robust alcohol dehydrogenase with 2-propanol as cheap cosubstrate. The complete conversion and high enantiopurity (ee > 99 %) of the products, demonstrated it as an ideal alternative for asymmetric synthesis of chiral amino acid compounds.
Zhou, Haisheng,Meng, Lijun,Yin, Xinjian,Liu, Yayun,Xu, Gang,Wu, Jianping,Wu, Mianbin,Yang, Lirong
supporting information
p. 6470 - 6477
(2019/11/02)

Stereoselective Synthesis of syn -γ-Hydroxynorvaline and Related α-Amino Acids
The total syntheses of three enantiomerically pure non-proteinogenic amino acids, l -norvaline, γ-oxonorvaline, and syn -γ-hydroxynorvaline, are reported. The chromatography-free route pivoted on the construction of highly enantiomerically enriched substituted α-amino-γ-oxopentanoic acid, from which all three members were accessed divergently via chemoselective and stereoselective reductions. The rapid synthesis of this key α-amino-γ-oxopentanoic acid was achieved by a highly diastereoselective crystallisation-driven three-component Mannich reaction from the readily available building blocks acetone, glyoxylic acid monohydrate, and (S)-(4-methoxyphenyl)ethylamine. The enantiomeric purity of all target molecules was confirmed by HPLC analysis, either of the amino acids or their derivatives.
Berke?, Du?an,Caletková, O?ga,Ferko, Branislav,Jakubec, Pavol,Kolarovi?, Andrej,Puch?ová, Eva,Valachová, Dominika
p. 4568 - 4575
(2019/12/11)

Sustainable and Continuous Synthesis of Enantiopure l-Amino Acids by Using a Versatile Immobilised Multienzyme System
The enzymatic synthesis of α-amino acids is a sustainable and efficient alternative to chemical processes, through which achieving enantiopure products is difficult. To more address this synthesis efficiently, a hierarchical architecture that irreversibly co-immobilises an amino acid dehydrogenase with polyethyleneimine on porous agarose beads has been designed and fabricated. The cationic polymer acts as an irreversible anchoring layer for the formate dehydrogenase. In this architecture, the two enzymes and polymer colocalise across the whole microstructure of the porous carrier. This multifunctional heterogeneous biocatalyst was kinetically characterised and applied to the enantioselective synthesis of a variety of canonical and noncanonical α-amino acids in both discontinuous (batch) and continuous modes. The co-immobilised bienzymatic system conserves more than 50 % of its initial effectiveness after five batch cycles and 8 days of continuous operation. Additionally, the environmental impact of this process has been semiquantitatively calculated and compared with the state of the art.
Velasco-Lozano, Susana,da Silva, Eunice S.,Llop, Jordi,López-Gallego, Fernando
p. 395 - 403
(2017/11/13)

Driving Transamination Irreversible by Decomposing Byproduct Α-Ketoglutarate into Ethylene Using Ethylene-Forming Enzyme
The transformations of transaminases have been extensively studied as an approach to the production of chiral amino moieties. However, the low equilibrium conversion of the reaction is a critical disadvantage to transaminase application, and a strategy for shifting the reaction equilibrium is essential. Herein, we have developed a novel method to effectively prevent the reversibility of transamination by fully decomposing byproduct α-ketoglutarate into ethylene and carbon dioxide in situ using ethylene-forming enzyme (EFE). Two transaminases and one EFE were expressed in E. coli and purified to be used in the cascade reaction. After optimal reaction conditions were determined based on the enzymatic properties, a cascade reaction coupling transaminase with EFE was conducted and showed high efficiency in the synthesis of l-phosphinothricin. Finally, using this approach with only an equivalent amount of amino donor l-glutamate increased the conversions of various keto acids from 99%. This strategy shows great potential for transamination using glutamate as the amino donor.
Meng, Li-Jun,Liu, Ya-Yun,Zhou, Hai-Sheng,Yin, Xin-Jian,Wu, Jian-Ping,Wu, Mian-Bin,Xu, Gang,Yang, Li-Rong
p. 3309 - 3314
(2018/10/02)

One-Pot Preparation of d-Amino Acids Through Biocatalytic Deracemization Using Alanine Dehydrogenase and Ω-Transaminase
d-Amino acids are pharmaceutically important building blocks, leading to a great deal of research efforts to develop cost-effective synthetic methods. Preparation of d-amino acids by deracemization has been conceptually attractive owing to facile synthesis of racemic amino acids by Strecker synthesis. Here, we demonstrated biocatalytic deracemization of aliphatic amino acids into d-enantiomers by running cascade reactions; (1) stereoinversion of l-amino acid to a d-form by amino acid dehydrogenase and ω-transaminase and (2) regeneration of NAD+ by NADH oxidase. Under the cascade reaction conditions containing 100?mM isopropylamine and 1?mM NAD+, complete deracemization of 100?mM dl-alanine was achieved after 24?h with 95% reaction yield of d-alanine (> 99% eeD, 52% isolation yield). Graphical Abstract: [Figure not available: see fulltext.].
Han, Sang-Woo,Shin, Jong-Shik
p. 3678 - 3684
(2018/10/20)

Development of a multi-enzymatic desymmetrization and its application for the biosynthesis of L-norvaline from DL-norvaline
Perindopril is an effective antihypertensive drug in strong demand used to treat hypertension. L-norvaline is a vital intermediate of Perindopril production mainly produced by chemical synthesis with low purity. We developed an environmentally friendly method to produce L-norvaline with high purity based on a desymmetrization process. D-Norvaline was oxidized to the corresponding keto acid by D-amino acid oxidase from the substrate DL-norvaline. Asymmetric hydrogenation of the keto acid to L-norvaline was carried out by leucine dehydrogenase with concomitant oxidation of NADH to NAD+. A NADH regeneration system was introduced by overexpressing a formate dehydrogenase. The unwanted H2O2by-product generated during D-norvaline oxidation was removed by adding catalase. A total of 54.09?g/L of L-norvaline was achieved, with an enantiomeric excess over 99% under optimal conditions, with a 96.7% conversion rate. Our desymmetrization method provides an environmental friendly strategy for the production of enantiomerically pure L-norvaline in the pharmaceutical industry.
Qi, Yunlong,Yang, Taowei,Zhou, Junping,Zheng, Junxian,Xu, Meijuan,Zhang, Xian,Rao, Zhiming,Yang, Shang-Tian
p. 104 - 109
(2017/03/23)

Efficient Enzymatic Preparation of13N-Labelled Amino Acids: Towards Multipurpose Synthetic Systems
Nitrogen-13 can be efficiently produced in biomedical cyclotrons in different chemical forms, and its stable isotopes are present in the majority of biologically active molecules. Hence, it may constitute a convenient alternative to Fluorine-18 and Carbon-11 for the preparation of positron-emitter-labelled radiotracers; however, its short half-life demands for the development of simple, fast, and efficient synthetic processes. Herein, we report the one-pot, enzymatic and non-carrier-added synthesis of the13N-labelled amino acids l-[13N]alanine, [13N]glycine, and l-[13N]serine by using l-alanine dehydrogenase from Bacillus subtilis, an enzyme that catalyses the reductive amination of α-keto acids by using nicotinamide adenine dinucleotide (NADH) as the redox cofactor and ammonia as the amine source. The integration of both l-alanine dehydrogenase and formate dehydrogenase from Candida boidinii in the same reaction vessel to facilitate the in situ regeneration of NADH during the radiochemical synthesis of the amino acids allowed a 50-fold decrease in the concentration of the cofactor without compromising reaction yields. After optimization of the experimental conditions, radiochemical yields were sufficient to carry out in vivo imaging studies in small rodents.
da Silva, Eunice S.,Gómez-Vallejo, Vanessa,Baz, Zuri?e,Llop, Jordi,López-Gallego, Fernando
p. 13619 - 13626
(2016/09/13)

Asymmetric Transamination of α-Keto Acids Catalyzed by Chiral Pyridoxamines
A new type of novel chiral pyridoxamines 3a-g containing a side chain has been developed. The pyridoxamines displayed catalytic activity and promising enantioselectivity in biomimetic asymmetric transamination of α-keto acids, to give various α-amino acids in 47-90% yields with up to 87% ee's under very mild conditions. An interesting effect of the side chain on enantioselectivity was observed in the reaction.
Lan, Xiaoyu,Tao, Chuangan,Liu, Xuliang,Zhang, Aina,Zhao, Baoguo
supporting information
p. 3658 - 3661
(2016/08/16)

Method for synthesizing L-norvaline
The invention provides a method for synthesizing L-norvaline. The method comprises the following steps: 1, adding acetic acid into a reaction kettle, adding DL-norvaline and D-tartaric acid while stirring, heating to 80DEG C, adding salicylaldehyde, and maintaining the temperature in a range of 80-85DEG C for 10h; 2, cooling to 20-25DEG C after temperature maintenance, keeping the decreased temperature for 1h, and centrifuging to obtain crude L-norvaline and D-tartaric acid; 3, adding petroleum ether to the crude L-norvaline and D-tartaric acid, stirring and washing for 30min, and centrifuging to obtain a purified L-norvaline and D-tartaric acid double salt; 4, heating the double salt in water to 70DEG C in order to completely dissolve the double salt, adjusting the pH value to 7 by using ammonia water, cooling to 20-25DEG C, crystallizing for 2h, centrifuging, and rinsing by using methanol to obtain crude L-norvaline; and 5, heating the crude L-norvaline in water to 80-85DEG C in order to completely dissolve the crude L-norvaline, adding active carbon, decoloring for 1h, filtering, concentrating, cooling to 20-25DEG C, crystallizing for 3h, centrifuging, rinsing with water to obtain wet L-norvaline, and carrying out 60DEG C vacuum drying to obtain dry L-norvaline. The method has the advantages of few steps, good environmental protection property and high yield.
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Paragraph 0011

(2016/10/17)

Biocatalytic cascade reactions for asymmetric synthesis of aliphatic amino acids in a biphasic reaction system
Abstract Enantiopure aliphatic amino acids, including l-3-hydroxyadamantylglycine (l-Hag), l-tert-leucine (l-Tle) and l-norvaline, are essential chiral building blocks for a number of pharmaceutical drugs. Here, we developed cascade enzyme reactions in an extractive biphasic system using a branched-chain amino acid transaminase (BCTA) and an (S)-selective ω-transaminase (ω-TA) for asymmetric synthesis of the aliphatic amino acids from achiral α-keto acid precursors. The extractive cascade reactions enabled equilibrium shift of the BCTA reaction by recycling an amino acid cosubstrate as well as acceleration of the ω-TA reaction by removing an inhibitory ketone product from an aqueous phase. Starting with 20 mM α-keto acid, 4 mM rac-homoalanine and 50 mM rac-α-methylbenzylamine (rac-α-MBA), the biphasic cascade reactions afforded synthesis of four unnatural amino acids (i.e., l-Tle, l-Hag, l-norvaline and l-norleucine) and two natural amino acids (i.e., l-valine and l-Leucine) with >92% conversion yield and >99.9% ee. To demonstrate the industrial feasibility of the extractive cascade reaction, preparative-scale synthesis of l-Hag was performed in a reaction mixture consisting of 300 mL hexane and 50 mL aqueous solution (50 mM phosphate buffer, pH 7.0) charged with 50 mM keto acid substrate, 5 mM l-homoalanine, 120 mM rac-α-MBA, 2 U/mL BCTA and 16 U/mL ω-TA. Conversion yield of l-Hag reached 92% with >99.9% ee at 70 h. Product isolation led to 0.32 g white solid of l-Hag (62 % isolation yield).
Park, Eul-Soo,Shin, Jong-Shik
p. 9 - 14
(2015/08/18)

The specificity and kinetic mechanism of branched-chain amino acid aminotransferase from Escherichia coli studied with a new improved coupled assay procedure and the enzyme's potential for biocatalysis
Branched-chain amino acid aminotransferase (BCAT) plays a key role in the biosynthesis of hydrophobic amino acids (such as leucine, isoleucine and valine), and its substrate spectrum has not been fully explored or exploited owing to the inescapable restrictions of previous assays, which were mainly based on following the formation/consumption of the specific branched-chain substrates rather than the common amino group donor/acceptor. In our study, detailed measurements were made using a novel coupled assay, employing (R)-hydroxyglutarate dehydrogenase from Acidaminococcus fermentans as an auxiliary enzyme, to provide accurate and reliable kinetic constants. We show that Escherichia coli BCAT can be used for asymmetric synthesis of a range of non-natural amino acids such as l-norleucine, l-norvaline and l-neopentylglycine and compare the kinetic results with the results of molecular modelling. A full two-substrate steady-state kinetic study for several substrates yields results consistent with a bi-bi ping-pong mechanism, and detailed analysis of the kinetic constants indicates that, for good 2-oxoacid substrates, release of 2-oxoglutarate is much slower than release of the product amino acid during the transamination reaction. The latter is in fact rate-limiting under conditions of substrate saturation.
Yu, Xuejing,Wang, Xingguo,Engel, Paul C.
p. 391 - 400
(2014/01/23)

Structural determinants for the non-canonical substrate specificity of the ω-transaminase from paracoccus denitrificans
Substrate binding pockets of ω-transaminase (ω-TA) consist of a large (L) pocket capable of dual recognition of hydrophobic and carboxyl substituents, and a small (S) pocket displaying a strict steric constraint that permits entry of a substituent no larger than an ethyl group. Despite the unique catalytic utility of ω-TA enabling asymmetric reductive amination of carbonyl compounds, the severe size exclusion occurring in the S pocket has limited synthetic applications of ω-TA to access structurally diverse chiral amines and amino acids. Here we report the first example of an ω-TA whose S pocket shows a non-canonical steric constraint and readily accommodates up to an n-butyl substituent. The relaxed substrate specificity of the (S)-selective ω-TA, cloned from Paracoccus denitrificans (PDTA), afforded efficient asymmetric syntheses of unnatural amino acids carrying long alkyl side chains such as lnorvaline and l-norleucine. Molecular modeling using the recently released X-ray structure of PDTA could pinpoint an exact location of the S pocket which had remained dubious. Entry of a hydrophobic substituent in the L pocket was found to have the S pocket accept up to an ethyl substituent, reminiscent of the canonical steric constraint. In contrast, binding of a carboxyl group to the L pocket induced a slight movement of V153 away from the small-pocketforming residues. The resulting structural change elicited excavation of the S pocket, leading to formation of a narrow tunnel-like structure allowing accommodation of linear alkyl groups of carboxylatebearing substrates. To verify the active site model, we introduced site-directed mutagenesis to six active site residues and examined whether the point mutations alleviated the steric constraint in the S pocket. Consistent with the molecular modeling results, the V153A variant assumed an elongated S pocket and accepted even an n-hexyl substituent. Our findings provide precise structural information on substrate binding to the active site of ω-TA, which is expected to benefit rational redesign of substrate specificity of ω-TA.
Park, Eul-Soo,Park, Sae-Rom,Han, Sang-Woo,Dong, Joo-Young,Shin, Jong-Shik
p. 212 - 220
(2014/03/21)

Amidohydrolase Process: Expanding the use of l-N-carbamoylase/N-succinyl- amino acid racemase tandem for the production of different optically pure l-amino acids
A bienzymatic system comprising an N-succinylamino acid racemase from Geobacillus kaustophilus CECT4264 (GkNSAAR) and an enantiospecific l-N-carbamoylase from Geobacillus stearothermophilus CECT43 (BsLcar) has been developed. This biocatalyst has been able to produce optically pure natural and non-natural l-amino acids starting from racemic mixtures of N-acetyl-, N-formyl- and N-carbamoyl-amino acids by dynamic kinetic resolution. The fastest conversion rate was found with N-formyl-amino acids, followed by N-carbamoyl- and N-acetyl-amino acids, and GkNSAAR proved to be the limiting step of the system due to its lower specific activity. Metal ion cobalt was essential for the activity of the biocatalyst and the system was optimally active when Co 2+ was added directly to the reaction mixture. The optimum pH for the biocatalyst proved to be 8.0, for both N-formyl- and N-carbamoyl-amino acid substrates, whereas optimum temperature ranges were 45-55 °C for N-formyl-amino acids and 55-70 °C for N-carbamoyl-derivatives. The bienzymatic system was equally efficient in converting aromatic and aliphatic substrates. Total conversion was also achieved using high substrate concentrations (100 and 500 mM) with no noticeable inhibition. This "Amidohydrolase Process" enables the production of both natural and non-natural l-amino acids from a broad substrate spectrum with yields of over 95%.
Soriano-Maldonado, Pablo,Rodríguez-Alonso, María José,Hernández-Cervantes, Carmen,Rodríguez-García, Ignacio,Clemente-Jiménez, Josefa María,Rodríguez-Vico, Felipe,Martínez-Rodríguez, Sergio,Las Heras-Vázquez, Francisco Javier
p. 1281 - 1287
(2014/07/22)

Deracemization of amino acids by coupling transaminases of opposite stereoselectivity
Biocatalytic deracemization of amino acids without relying on oxidase-based deamination of an unwanted enantiomer was demonstrated by coupling a-and w-transaminases displaying opposite stereoselectivity. This strategy employs isopropylamine and a keto acid as cosubstrates and is free of generation of hydrogen peroxide which is troublesome in the conventional oxidase-based methods.
Park, Eul-Soo,Shin, Jong-Shik
p. 3505 - 3509
(2015/02/19)

Large α-aminonitrilase activity screening of nitrilase superfamily members: Access to conversion and enantiospecificity by LC-MS
A high-throughput screening for the identification of nitrilases demonstrating activity towards alpha-aminonitriles is reported. A LC-MS assay giving access to both conversion and enantiospecificity was developed. 588 candidate enzymes were screened as cell lysates against six alpha-aminonitriles in 96-well microplates. The candidate enzymes were selected following two criteria, their sequence identity with a set of known nitrilases or their phylogenetic position among the nitrilase superfamily. Five enzymes were identified and found to hydrolyse alpha-aminonitrile into the corresponding alpha-aminoacid. The substrate range was found to be very narrow as only two different alpha-aminonitriles, 2-aminovaleronitrile and 2-amino-2- phenylacetonitrile, were found to be substrates. The biocatalytic capabilities of three enzymes were further investigated and the best result was obtained with an enzyme from Burkholderia xenovorans catalysing the enantiospecific hydrolysis of 2-aminovaleronitrile into (S)-norvaline with excellent conversion and enantiomeric excess.
Bordier, Franck,Stam, Mark,Darii, Ekaterina,Tricot, Sabine,Fossey, Aurelie,Rohault, Johanna,Debard, Adrien,Mariage, Aline,Pellouin, Virginie,Petit, Jean-Louis,Perret, Alain,Vallenet, David,Salanoubat, Marcel,Weissenbach, Jean,Vergne-Vaxelaire, Carine,De Berardinis, Veronique,Zaparucha, Anne
p. 79 - 88
(2014/07/08)

Biocatalytic asymmetric synthesis of unnatural amino acids through the cascade transfer of amino groups from primary amines onto keto acids
Flee to the hills: An unfavorable equilibrium in the amino group transfer between amino acids and keto acids catalyzed by α-transaminases was successfully overcome by coupling with a ω-transaminase reaction as an equilibrium shifter, leading to efficient asymmetric synthesis of diverse unnatural amino acids, including L-tert-leucine and D-phenylglycine. Copyright
Park, Eul-Soo,Dong, Joo-Young,Shin, Jong-Shik
p. 3538 - 3542
(2014/01/06)

SEPARATING AGENT FOR CHROMATOGRAPHY
A separating agent for chromatography is provided that is useful for the separation of specific compounds, e.g., for the optical resolution of amino acids. This separating agent for chromatography provides a higher productivity and contains a crown ether-like cyclic structure and optically active binaphthyl. This separating agent for chromatography containing a crown ether-like cyclic structure and optically active binaphthyl is provided by introducing a substitution group for binding to carrier into a specific commercially available 1,1′-binaphthyl derivative that has substituents at the 2, 2′, 3, and 3′ positions, then introducing a crown ether-like cyclic structure, and subsequently chemically bonding the binaphthyl derivative to the carrier through the substitution group for binding to carrier.
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Paragraph 0074; 0075

(2013/08/15)

Efficient kinetic resolution of amino acids catalyzed by lipase AS 'Amano' via cleavage of an amide bond
Herein the efficient kinetic resolution of non-natural alpha-amino acids catalyzed by lipase AS 'Amano' via cleaving the amide bond is reported. The starting materials were the corresponding amino acid amides and the amino acids were generated with ees of up to 99% with E values of >600. These results indicated that the lipase AS 'Amano' could be a powerful amide hydrolase for the kinetic resolution of amino acid starting from the corresponding amino acid amides.
Wang, Bo,Liu, Yanfeng,Zhang, Dela,Feng, Yuhong,Li, Jiacheng
p. 1338 - 1342,5
(2020/09/16)

Simplifying pyridoxal: Practical methods for amino acid dynamic kinetic resolution
Figure presented Metal complexes of picolinaldehyde are identified as low-cost and environmentally benign catalysts, providing high reaction rates and turnovers for the racemization of amino acids. These pyridoxal surrogates demonstrate activity toward a variety of amino acid esters. Applications to chemoenzymatic dynamic kinetic resolutions provide access to amino acids in high yields and with excellent enantioselectivities, demonstrating their compatibility with protease-mediated transformations.
Felten, Albert E.,Zhu, Gangguo,Aron, Zachary D.
supporting information; experimental part
p. 1916 - 1919
(2010/07/06)

NOVEL IMIDAZOLIDINONE DERIVATIVE, METHOD OF PRODUCING THE SAME AND METHOD OF PRODUCING OPTICALLY ACTIVE AMINO ACID
The objective of the present invention is to provide an optically active imidazolidinone derivative widely usable for synthesizing an optically active amino acid, a method of easily producing the derivative, and a method of easily producing an optically active amino acid by using the derivative. The objective can be achieved by producing an optically active amino acid using a novel optically active imidazolidinone derivative represented by a general formula (3) and the like. According to the method of the present invention, an optically active imidazolidinone derivative can be obtained by preferential crystallization from a mixture of isomers of the imidazolidinone derivative. Therefore, an optically active amino acid can be easily and stereoselectively produced without cumbersome procedures required for the conventional methods, such as resolution of diastereomers, synthesis from an optically active amino acid and resolution of isomers by silica gel column cromatography.
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Page/Page column 31-32

(2009/05/29)

Dynamic Kinetic resolution of α-amino acid esters in the presence of aldehydes
A convenient procedure for the racemization of α-amino acid esters in the presence of catalytic amounts of salicylaldehydes is described. The combination of this racemization protocol with lipase-catalyzed ester hydrolysis allows successful dynamic kinetic resolution of various α-amino acid esters. The corresponding α-amino acids are obtained in high yield and optical purity. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Schichl, Daniel A.,Enthaler, Stephan,Holla, Wolfgang,Riermeier, Thomas,Kragl, Udo,Beller, Matthias
scheme or table
p. 3506 - 3512
(2009/04/07)

Resolution of non-protein amino acids via the microbial protease-catalyzed enantioselective hydrolysis of their N-unprotected esters
In the Aspergillus oryzae protease-catalyzed ester hydrolysis, substitution of N-unprotected amino acid esters for the corresponding N-protected amino acid esters resulted in a large enhancement of the hydrolysis rate, while the enantioselectivity was deteriorated strikingly when the substrates employed were the conventional methyl esters. This difficulty was overcome by employing esters bearing a longer alkyl chain such as the isobutyl ester. Utilizing this ester, amino acids carrying an aromatic side chain were resolved with excellent enantioselectivities (E=50 to >200). With amino acids bearing an aliphatic side chain also, good results in terms of the hydrolysis rate and enantioselectivity were obtained by employing such an ester as the isobutyl ester. Moreover, the enantioselectivity proved to be enhanced further by conducting the reaction at low temperature. This procedure was applicable to the case where the enantioselectivity was not high enough even by the use of the isobutyl ester.
Miyazawa, Toshifumi,Imagawa, Kiwamu,Minowa, Hiroe,Miyamoto, Toyoko,Yamada, Takashi
p. 10254 - 10261
(2007/10/03)

Asymmetric Strecker synthesis by addition of trimethylsilyl cyanide to aldehyde SAMP-hydrazones
The asymmetric 1,2-addition of trimethylsilyl cyanide to aldehyde SAMP-hydrazones in the presence of titanium tetrachloride and diethylether in dichloromethane at -100°C up to room temperature, removal of the chiral auxiliary and acid hydrolysis affords α-amino acids in high enantiomeric excesses (ee=94-97%).
Enders, Dieter,Moser, Michael
p. 8479 - 8481
(2007/10/03)

Stereodivergent addition of allylmetal reagents to imines derived from (R)2,3-Di-O-benzylglyceraldehyde by appropriate selection of metal and double stereodifferentiation
The addition of allylmetal reagents to N-benzylimines derived from (R)-2,3-di-O-benzylglyceraldehyde has been achieved with high yields and diastereoselectivities. Homoallylamine 2a of syn configuration is obtained preferentially with allylmagnesium bromide, whereas homoallylamine 2a of anti configuration is obtained as the major reaction product with allyl-9-borabicyclo[3.3.1]nonane. Appropriate combinations of the allylmetal reagent and imines derived from (R)-2,3-di-O-benzylglyceraldehyde and (S)- or (R)-1-phenylethylamine afforded syn or anti homoallylamines with total stereocontrol through double stereodifferentiation processes. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Badorrey, Ramon,Cativiela, Carlos,Diaz-de-Villegas, Maria D.,Diez, Roberto,Galvez, Jose A.
p. 3763 - 3767
(2007/10/03)

Rapid microwave-assisted deprotection of N-Cbz and N-Bn derivatives
Catalytic-transfer hydrogenation in iso-propanol under microwave irradiation has been performed to rapidly deprotect N-Cbz and N-Bn derivatives. The method is particularly suitable for the synthesis of short peptides and can also be carried out on supported molecules. The rapid cleavage of chiral molecules derived from (S)-1-phenylethylamine can be very useful for asymmetric synthesis of nitrogen containing compounds.
Daga, Maria Caterina,Taddei, Maurizio,Varchi, Greta
p. 5191 - 5194
(2007/10/03)

Chemo-enzymatic synthesis of optically active amino acids and peptides
The industrial alkaline protease, alcalase, is stable and active in a high concentration of organic solvents and useful as a biocatalyst for (i) diastereoselective hydrolysis of peptide esters and preparation of racemization-free peptides; (ii) selective incorporation of esters of D-amino acid into peptides in t-butanol via a selective hydrolysis of esters of D,L-amino acid, followed by using the unhydrolyzed D-esters as a nucleophile in a kinetically controlled peptide bond formation; (iii) resolution of esters of amino acid in 95% t-butanol/5% water, followed by saponification of the unreacted esters to offer both enantiomers with high yield and optical purity; (iv) completely resolve amino-acid esters with high yield and optical purity via in situ racemization of the unreacted antipode catalyzed by pyridoxal 5-phosphate; (v) cryobioorganic synthesis of peptides with increased yields 15%-40% of peptide bond formation by reaction at 5 °C instead of 25-30 °C of a kinetically controlled enzymatic reaction in alcohols.
Chen, Shui-Tein,Wang, Kung-Tsung
p. 301 - 311
(2007/10/03)

Acylase I-catalyzed deacetylation of N-acetyl-L-cysteine and S-alkyl-N- acetyl-L-cysteines
The aminoacylase that catalyzes the hydrolysis of N-acetyl-L-cysteine (NAC) was identified as acylase I after purification by column chromatography and electrophoretic analysis. Rat kidney cytosol was fractionated by ammonium sulfate precipitation, and the proteins were separated by ion-exchange column chromatography, gel-filtration column chromatography, and hydrophobic interaction column chromatography. Acylase activity with NAC and N-acetyl-L- methionine (NAM), a known substrate for acylase I, as substrates coeluted during all chromatographic steps. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the protein was purified to near homogeneity and had a subunit M(r) of 43 000, which is identical with the M(r) of acylase I from porcine kidney and bovine liver. n-Butylmalonic acid was a slow-binding inhibitor of acylase I and inhibited the deacetylation of NAC with a K(i) of 192 ± 27 μM. These results show that acylase I catalyzes the deacetylation of NAC. The acylase I-catalyzed deacetylation of a range of S-alkyl-N- acetyl-L-cysteines, their carbon and oxygen analogues, and the selenium analogue of NAM was also studied with porcine kidney acylase I. The specific activity of the acylase I-catalyzed deacetylation of these substrates was related to their calculated molar volumes and log P values. The S-alkyl-N- acetyl-L-cysteines with short (C0-C3) and unbranched S-alkyl substituents were good acylase I substrates, whereas the S-alkyl-N-acetyl-L-cysteines with long (>C3) and branched S-alkyl substituents were poor acylase I substrates. The carbon and oxygen analogues of S-methyl-N-acetyl-L-cysteine and the carbon analogue of S-ethyl-N-acetyl-L-cysteine were poor acylase I substrates, whereas the selenium analogue of NAM was a good acylase I substrate.
Uttamsing, Vinita,Keller,Anders
p. 800 - 809
(2007/10/03)

2-oxoethyl derivatives as immunosuppressants
A class of compounds that suppress human T-lymphocyte proliferation is disclosed. The active compounds essentially contain at least the following structure: STR1
-
(2008/06/13)

Asymmetric synthesis of α-amino acids via diastereoselective addition of (R)-pantolactone to their ketenes
The diastereoselective addition of (R)-pantolactone to various amino ketenes derived from phthalylamino acids is reported. The configuration of the newly-generated asymmetric center is dependent on alkyl or aryl C(x substitution. This method constitutes a novel and convenient way of amino acid deracemization.
Calmes, Monique,Daunis, Jacques,Mai, Nathalie
p. 1641 - 1648
(2007/10/03)

Optimisation of the retroracemisation procedure for α-amino acids using (S)-2-[(N-alkylprolyl)amino]benzophenones, recyclable chiral axiliaries
The retroracemisation procedure developed by Belokon and coworkers has been re-examined using a variety of new (S)-2-[N-alkylprolyl)amino]benzophenone chiral auxiliaries. It has been found that (S)-2-[(N-benzylprolyl)amino] and (S)-2-[(N-1-(naphthalenyl-1-methyl)prolyl)amino] benzophenones ((S)-BPB and (S)-NPB) when used in conjunction with Ni(NO3)2·6H2O and a racemic α-amino acid preferentially form a single diastereoisomer in the presence of a mild base such as sodium methoxide. Decomposition of this complex under acidic conditions leads to the isolation of the (S)-amino acid in good yield, and in 55 to 99% e.e. The retroracemisation abilities of a polymer supported form of the (S)-BPB ligand have also been investigated and preliminary results for this are presented here.
De, Binod B.,Thomas, Neil R.
p. 2687 - 2691
(2007/10/03)

Resolution of non-protein amino acids via microbial protease-catalyzed ester hydrolysis: Marked enhancement of enantioselectivity by the use of esters with longer alkyl chains and at low temperature
In the microbial protease-catalyzed hydrolysis of amino acid esters with the free α-amino group, the enantioselectivity can be enhanced greatly by employing esters with longer alkyl chains such as the isobutyl ester instead of the conventional methyl ester and by conducting the reaction at low temperature.
Miyazawa, Toshifumi,Minowa, Hiroe,Miyamoto, Toyoko,Imagawa, Kiwamu,Yanagihara, Ryoji,Yamada, Takashi
p. 367 - 370
(2007/10/03)

L-Methionine related 1-amino acids by acylase cleavage of their corresponding N-acetyl-DL-derivatives
Acylase I from Aspergillus oryzae is an even more useful enzyme than suggested so far. Besides standard amino acids such as L-Met, L-Val and L-Phe, a number of additional sulfur- and selenium-containing amino acids can be obtained at useful reaction rates and in very high enantiomeric purity by kinetic resolution of the respective N-acetyl-DL-amino acids.
Bommarius, Andreas S.,Drauz, Karlheinz,Guenther, Kurt,Knaup, Guenter,Schwarm, Michael
p. 3197 - 3200
(2007/10/03)

Schiff bases of amino acid esters as new substrates for the enantioselective enzymatic hydrolysis and accompanied asymmetric transformations in aqueous organic solvents
The enzyme (lipases and chymotrypsin)-catalyzed hydrolysis of Schiff bases derived from racemic amino acid esters and aromatic aldehydes has been investigated. The reactions were successfully carried out in different aqueous organic solvents at ambient temperature, but the aqueous acetonitrile (5.4% water content by volume) was the solvent of choice. The L-amino acid (ee 98%) precipitated out from the solution as the reaction progressed, and the liberated aldehyde and unhydrolyzed D-ester (ee 40-98%) remained in the solution. The range of substrates included amino acids having different types of side chains. The addition of an organic base (DABCO) into the solution resulted in the racemization of the remaining D-ester and the additional hydrolysis of the substrate, thus leading to the effective asymmetric transformation of the initial ester. Upto 87.5% of the initial racemate was converted into the L-enantiomer.
Parmar, Virinder S.,Singh, Amarjit,Bisht, Kirpal S.,Kumar, Naresh,Belokon,Kochetkov,Ikonnikov,Orlova,Tararov,Saveleva
p. 1223 - 1226
(2007/10/03)

The asymmetric synthesis of allylglycine and other unnatural α-amino acid via zinc-mediated allylation of oximes in aqueous media
Enantiomerically pure or highly enriched allylglycine and its chain-substituted analogs are easily accessible from the reaction of the sultam derivative of O-benzyl glyoxylic acid oxime with allylic bromides in the presence of powdered zinc in aqueous ammonium chloride.
Hanessian, Stephen,Yang, Rui-Yang
p. 5273 - 5276
(2007/10/03)

Chemo-Enzymic Synthesis of Optically Active α,α-Disubstituted α-Amino Acids
A series of α,α-disubstituted α-amino esters was chemically synthesized and then resolved through enantioselective hydrolysis catalysed by a new enzyme isolated from crude Humicola langinosa lipase.This enzyme only accepts free amino esters as substrates with neither lipase activity toward olive oil nor esterase activity toward o-nitrophenyl butyrate.It is unique in that it successfully catalyses the resolution of amino esters with two large α-alkyl groups including aliphatic, aromatic and cyclic amino esters.Examples of resolutions where the alkyl groups differ in size by as little as a single carbon atom have been demonstrated.For determination of absolute configuration, some of the optically active α,α-disubstituted amino acids were also prepared through Schoellkopf's asymmetric synthesis and the structures were verified by X-ray crystallography.A model depicting the substrate binding site of the enzyme is proposed.
Liu, Weiguo,Ray, Paul,Benezra, Steven A.
p. 553 - 560
(2007/10/02)

Asymmetric synthesis of α-amino acids by copper-catalyzed conjugate addition of Grignard reagents to optically active carbamatoacrylates
Optically active ene carbamates were α-lithiated by lithium tetramethylpiperidide in the presence of trialkylstannyl chlorides to produce α-stannylated compounds. These underwent facile palladium-catalyzed couplings with acid chlorides to produce α-keto ene carbamates in good yield. Treatment of the α-stannyl ene carbamates with butyllithium followed by quenching with carbon dioxide and esterification gave optically active carbamatoacrylates. Copper-catalyzed addition of tert-butyl-, 1-naphthyl-, 2-propenyl-, p-methoxyphenyl-, (trimethylsilyl)methyl-, cyclohexyl-, 1-adamantyl-, and isopropyl Grignard reagents followed by quenching at -10 to 25°C and removal of the protecting groups gave the corresponding α-amino acids in 70-90% yield and 73-97% ee. Quenching the reaction at low temperature resulted in little if any asymmetric induction.
Lander, Peter A.,Hegedus, Louis S.
p. 8126 - 8132
(2007/10/02)

Resolution of amino acids in a mixture of 2-methyl-2-propanol/water (19:1) catalyzed by alcalase via in situ racemization of one antipode mediated by pyridoxal 5-phosphate
Procedures for the conversion of a racemic amino acid into the L-enantiomer by the alcalase catalyzed resolution of the amino acid ester in 2-methyl-2-propanol/water (19:1) simultaneously with the pyridoxal 5-phosphate-catalyzed racemization of the unhydrolyzed antipode have been developed.
Chen,Huang,Wang
p. 7580 - 7581
(2007/10/02)

ASYMMETRIC SYNTHESIS USING ENANTIOPURE SULFINIMINES: A CONVENIENT SYNTHESIS OF α-AMINO ACIDS
Diethylaluminum cyanide adds stereoselectively to enantiopure sulfinimines 1 and 2 to give diastereomerically enriched α-amino nitriles 3 and 4 which are hydrolyzed in one step to α-amino acids 5 in >95percent ee and good yields.
Davis, Franklin A.,Reddy, Rajarathnam E.,Portonovo, Padma S.
p. 9351 - 9354
(2007/10/02)

Amino Acid Synthesis via Ring Opening of N-Sulphonyl Aziridine-2-Carboxylate Esters with Organometallic Reagents.
Nucleophilic ring opening of optically active N-sulphonyl aziridine-2-carboxylate esters with organometallic reagents has been investigated as a method of preparation of optically active amino acids.Key Words: aziridine-2-carboxylate, cuprate, nucleophilic ring opening, amino acid
Baldwin, Jack E.,Spivey, Alan C.,Schofield, Christopher J.,Sweeney, Joseph B.
p. 6309 - 6330
(2007/10/02)

Efficient asymmetric synthesis of amino acids through hydrogenation of the didehydroamino acid residue in cyclic imino-ester derivatives
The trisubstituted olefinic bond of chiral cyclic α,β-didehydroamino acid derivatives was hydrogenated in the presence of Pd/C with >95% diastereoface discrimination to give, after hydrolysis, the corresponding S-amino acids. The reduction of the double bond with L-selectride does not change the orientation of diastereoface discrimination and the diastereoselectivity is still high.
Cativiela,Diaz-de-Villegas,Galvez
p. 567 - 572
(2007/10/02)

The Ring Opening of Aziridine-2-carboxylate Esters with Organometallic Reagents
The ring opening of aziridines with organocuprate reagents provides a new entry to amino acids.
Baldwin, Jack E.,Adlington, Robert M.,O'Neil, Ian A.,Schofield, Christopher,Spivey, Alan C.,Sweeney, Joseph B.
p. 1852 - 1854
(2007/10/02)

Kinetic Resolution of Unnatural and Rarely Occuring Amino Acids: Enantioselective Hydrolysis of N-Acyl Amino Acids Catalyzed by Acylase I
Acylase I (aminoacylase; N-acylamino-acid amidohydrolase, EC 3.5.1.14, from porcine kidney and the fungus Aspergillus) is broadly applicable enzymatic catalyst for the kinetic resolution of unnatural and rarely occuring α-amino acids.Its enantioselectivity for the hydrolysis of N-acyl L-α-amino acids is nearly absolute, yet it accepts substrates having a wide range of structure and functionality.This paper reports the initial rates of enzyme-catalyzed hydrolysis of over 50 N-acyl amino acids and analogues, the stabilities of the enzymes in aqueous and aqueous/organic solutions, and the effects of different acyl groups and metal ions on the rates of enzymatic hydrolysis.Eleven α-amino and α-methyl α-amino acids were resolved on a 2-29-g scale.Crude L- and D-amino acid products had generally >90percent ee.The utility of resolved amino acids as chiral synthons was illustrated by the preparation of (R)- and (S)-1-butene oxide and the diastereoselective (cis:trans, 7-8:1) iodolactonization of three 2-amino-4-alkenoic acid derivatives.
Chenault, H. Keith,Dahmer, Juergen,Whitesides, George M.
p. 6354 - 6364
(2007/10/02)

STUDIES ON THE REACTION OF α-IMINO ESTERS WITH ORGANOMETALLIC COMPOUNDS
Benzylzinc reagent reacted with α-amino ester ( 2 ) at the α-carbon exclusively, though other organometallic reagents such as Mg, Al, Cu, Ti, and B derivatives reacted at the nitrogen atom.Use of the (S)-amine as a chiral auxiliary of 2 created the R chirality at the imino carbon.Very high chiral induction was realized in the reaction of prenylzinc reagent with α-imino 8-(-)phenylmenthyl ester ( 10 ).The reaction of 2 with heteroatom substituted allylic organometallic compounds ( 15 ) gave the corresponding α-heteroatom substituted amino acid derivatives ( 16 ).Here again, the allylic zinc reagent gave the adduct in higher yield than the corresponding Ti, Al, and B reagents.
Yamamoto, Yoshinori,Ito, Wataru
p. 5415 - 5424
(2007/10/02)

Practical Asymmetric Syntheses of α-Amino Acids through Carbon-Carbon Bond Constructions on Electrophilic Glycine Templates
The optically active D- and L-erythro-4-(benzyloxycarbonyl)-5,6-diphenyl-2,3,5,6-tetrahydro-4H-1,4-oxazin-2-ones (3) and D- and L-erythro-4-(tert-butoxycarbonyl)-5,6-diphenyl-2,3,5,6-tetrahydro-4H-1,4-oxazin-2-ones (3) can be efficiently brominated to serve as electrophilic glycine templates for the asymmetric synthesis of amino acids.It was found that coupling to these templates can proceed with either net retention or net inversion of stereochemistry.The final deblocking to the amino acids is accomplished with either dissolving-metal reduction or catalytic hydrogenolysis.The syntheses of β-ethyl aspartic acid, norvaline, allylglycine, alanine, norleucine, homophenylalanine, p-methoxyhomophenylalanine, cyclopentylglycine, and cyclopentenylglycine and a formal synthesis of clavalanine are described.In addition, the direct asymmetric syntheses of N-t-BOC-allylglycine and N-t-BOC-cyclopentenylglycine are described.
Williams, Robert M.,Sinclair, Peter J.,Zhai, Dongguan,Chen, Daimo
p. 1547 - 1557
(2007/10/02)

Racemic Structures of Organic Ammonium Salts of N-Acetyl-DL-2-aminobutyric Acid and N-Acetyl-DL-norvaline and Optical Resolution by Preferential Crystallization of DL-Ammonium Salts
The racemic structures of the ammonium salts (AM salts) and seven organic ammonium salts of N-acetyl-DL-2-aminobutyric acid (Dl-AcAbu) and N-acetyl-DL-norvaline (DL-AcNva) were studied on the basis of thermodynamic analyses to explore the possibility of optical resolution by preferential crystallization.An empirical equation has been derived from thermodynamic data and melting points of ammonium and organic ammonium salts of N-acyl-DL-amino acids to predict racemic structure around room temperature.The AM salts of DL-AcAbu and -AcNva exist in conglomerate around room temperature.It is possible to resolve optically these DL-AM salts by preferential crystallization in ethanol at 10 deg C, and the succesive preferential crystallization followed by purification gave D- and L-2-aminobutyric acids and -norvalines with optical purities close to 100percent.
Shiraiwa, Tadashi,Yoshida, Hirokazu,Tsuda, Makoto,Kurokawa, Hidemoto
p. 947 - 952
(2007/10/02)

Dehalogenation and Deamination of L-2-Amino-4-chloro-4-pentenoic Acid by Proteus mirabilis
Eighty-one strains of bacteria were tested for their ability to catalyze the release of chloride ion from DL-2-amino-4-chloro-4-pentenoic acid.A dehalogenating enzyme was obtained from the cells of Proteus mirablis IFO 3849, which can use the L-isomer.The enzyme was constitutively produced.The conversion of L-2-amino-4-chloro-4-pentenoic acid to 2-keto-4-pentenoic acid, ammonia, and chloride ion was demonstrated.The reaction product, 2-keto-4-pentenoic acid, was isolated as its 2,4-dinitrophenylhydrazone and identified by catalytic hydrogenolysis of the hydrazone to the corresponding amino acid, norvaline.
Moriguchi, Mitsuaki,Hoshino, Seiichi,Hatanaka, Shin-Ichi
p. 3295 - 3300
(2007/10/02)

APPLICATION OF E. COLI ASPARTATE TRANSAMINASE TO AMINO ACID SYNTHESIS
The kinetics and synthetic utility of the conversion of α-keto acids into L-α-amino acids using cloned E.coli Aspartate transaminase have been evaluated.
Baldwin, Jack E.,Dyer, Robert L.,Ng, Si C.,Pratt, Andrew J.,Russell, Mark A.
p. 3745 - 3746
(2007/10/02)