127-17-3Relevant articles and documents
Photocatalytic Conversion of Lactic Acid to Malic Acid through Pyruvic Acid in the Presence of Malic Enzyme and Semiconductor Photocatalysts
Inoue, Hiroshi,Yamachika, Mikio,Yoneyama, Hiroshi
, p. 2215 - 2220 (1992)
The photocatalytic fixation of CO2 in pyruvic acid to yield malic acid has been achieved in TiO2 microcrystal and CdS particle suspensions using malic enzyme as the catalyst, methyl viologen as the electron mediator and either 2-mercaptoethanol or lactic acid as the hole scavenger.The evaluation of the rate-determining step in the photocatalytic fixation reaction was made at the TiO2 microcrystal for the case of 2-mercaptoethanol as the hole scavenger.The use of lactic acid as the hole scavenger resulted in the selective photoproduction of pyruvic acid at the CdS photocatalyst, a fraction of which was then converted into malic acid by reductive CO2 fixation at the malic enzyme.However, it has been found that lactic acid causes a decrease in the catalytic activities of the enzyme, the degree depending on the relative concentrations of malic enzyme and lactic acid.
Oxidation of methylmalonic acid by cerium(IV). Evidence for parallel reaction pathways
Kvernberg, Per Olav,Hansen, Eddy W.,Pedersen, Bjorn,Rasmussen, Asbjorn,Ruoff, Peter
, p. 2327 - 2331 (1997)
The reaction between methylmalonic acid (MeMA) and Ce(IV) ion in 1 M sulfuric acid/D2SO4 has been studied by means of 1H- and 13C-NMR. When MeMA is in excess, acetic acid, hydroxymethylmalonic acid, and pyruvic acid are formed as stable end products. When Ce(IV) is in stoichiometric excess, acetic acid is the only product. Approximately 70-80% of the MeMA forms rapidly acetic acid with hydroxymethylmalonic acid and pyruvic acid as reactive intermediates. The remaining MeMA reacts along parallel pathways and forms two intermediates, which slowly convert to hydroxymethylmalonic acid and pyruvic acid, respectively.
Photooxidation of 2-Hydroxy Acids by Copper(II) Species in Aqueous Solution
Matsushima, Ryoka,Ichikawa, Yoshinori,Kuwabara, Katsuyuki
, p. 1902 - 1907 (1980)
Ultraviolet irradiation of aqueous lactic, glycolic, or 2-hydroxybutanoic acid in the presence of copper (II) leads to photoredox reaction to give corresponding α-keto acid, aldehyde with evolution of carbon dioxide, and the precipitate of copper (I).The mole ratio of the carbonyl products to the consumption of copper(II) is close to 0.5.Oxidative decarboxylation dominates at pH above 1 while the formation of α-keto acids favors at lower pH.The formation of α-keto acids is selectivity suppressed by the addition of free radical scavengers.Free radical oxidations of the acids with bromine atom or benzoyl radicals give exclusively α-keto acids.The reaction mechanism has been discussed.
Immobilization of thermotolerant intracellular enzymes on functionalized nanoporous activated carbon and application to degradation of an endocrine disruptor: kinetics, isotherm and thermodynamics studies
Saranya,Ranjitha,Sekaran
, p. 66239 - 66259 (2015)
A bacterium, Serratia marcescens capable of degrading the endocrine disruptor, 2-nitrophloroglucinol (NPG) was isolated from tannery wastewater contaminated soil. The mixed intracellular enzymes (MICE) produced from S. marcescens were extracted and characterized. The functionalized nanoporous activated carbon matrix (FNAC) was prepared to immobilize MICE. The optimum conditions for the immobilization of MICE on FNAC were found to be time, 2.5 h; pH, 7.0; temperature, 40°C; concentration of MICE, 4 mg; particle size of FNAC, 300 μm and mass of FNAC, 1 g. The FNAC materials before and after immobilization of MICE were characterized using scanning electron microscopy, Fourier transform-infrared spectrophotometry and an X-ray diffractometer. The thermal behaviour of the free and the immobilized MICE was studied using thermogravimetric analysis. The immobilization of MICE on FNAC obeyed the Freundlich model and the immobilization process followed a pseudo second order kinetic model. MICE-FNAC matrix was used to degrade NPG in aqueous solution. The degradation of NPG by MICE-FNAC was optimum at contact time, 3 h; pH, 7.0; temperature, 40°C; concentration of NPG, 20 μM and agitation speed, 70 rpm. The degradation of NPG was found to be enhanced in the presence of Zn2+, Cu2+, Ca2+ and V3+ ions. The degradation of NPG by MICE-FNAC was studied using UV-visible, fluorescence and FTIR spectroscopy. The degradation of NPG by MICE-FNAC was confirmed using HPLC, NMR and GC-MS spectroscopy.
Crystal structure of D-serine dehydratase from Escherichia coli
Urusova, Darya V.,Isupov, Michail N.,Antonyuk, Svetlana,Kachalova, Galina S.,Obmolova, Galina,Vagin, Alexei A.,Lebedev, Andrey A.,Burenkov, Gleb P.,Dauter, Zbigniew,Bartunik, Hans D.,Lamzin, Victor S.,Melik-Adamyan, William R.,Mueller, Thomas D.,Schnackerz, Klaus D.
, p. 422 - 432 (2012)
D-Serine dehydratase from Escherichia coli is a member of the β-family (fold-type II) of the pyridoxal 5′-phosphate-dependent enzymes, catalyzing the conversion of D-serine to pyruvate and ammonia. The crystal structure of monomeric D-serine dehydratase has been solved to 1.97 A-resolution for an orthorhombic data set by molecular replacement. In addition, the structure was refined in a monoclinic data set to 1.55 A resolution. The structure of DSD reveals a larger pyridoxal 5′-phosphate- binding domain and a smaller domain. The active site of DSD is very similar to those of the other members of the β-family. Lys118 forms the Schiff base to PLP, the cofactor phosphate group is liganded to a tetraglycine cluster Gly279-Gly283, and the 3-hydroxyl group of PLP is liganded to Asn170 and N1 to Thr424, respectively. In the closed conformation the movement of the small domain blocks the entrance to active site of DSD. The domain movement plays an important role in the formation of the substrate recognition site and the catalysis of the enzyme. Modeling of D-serine into the active site of DSD suggests that the hydroxyl group of D-serine is coordinated to the carboxyl group of Asp238. The carboxyl oxygen of D-serine is coordinated to the hydroxyl group of Ser167 and the amide group of Leu171 (O1), whereas the O2 of the carboxyl group of D-serine is hydrogen-bonded to the hydroxyl group of Ser167 and the amide group of Thr168. A catalytic mechanism very similar to that proposed for L-serine dehydratase is discussed.
Exploration of Transaminase Diversity for the Oxidative Conversion of Natural Amino Acids into 2-Ketoacids and High-Value Chemicals
Chen, Yanchun,Cui, Xuexian,Cui, Yinglu,Li, Chuijian,Li, Ruifeng,Li, Tao,Sun, Jinyuan,Wu, Bian,Zhu, Tong
, p. 7950 - 7957 (2020)
The use of 2-ketoacids is very common in feeds, food additives, and pharmaceuticals, and 2-ketoacids are valuable precursors for a plethora of chemically diverse compounds. Biocatalytic synthesis of 2-ketoacids starting from l-amino acids would be highly desirable because the substrates are readily available from biomass feedstock. Here, we report bioinformatic exploration of a series of aminotransferases (ATs) to achieve the desired conversion. Thermodynamic control was achieved by coupling an l-glutamate oxidation reaction in the cascade for the recycling of the amine acceptor. These enzymes were able to convert a majority of proteinogenic amino acids into the corresponding 2-ketoacids with high conversion (up to 99percent) and atom-efficiency. Furthermore, this enzyme cascade was extendable, and one-pot two-step processes were established for the synthesis of d-amino acids and N-methylated amino acids, achieving great overall conversion (up to 99percent) and high ee values (>99percent). These developed enzymatic methodologies offer convenient routes for utilizing amino acids as synthetic reagents.
Oxidation of lactic acid by water soluble (Colloidal) manganese dioxide
Khan, Zaheer,Raju,Akram, Mohd,Kabir-Ud-Din
, p. 359 - 366 (2004)
Spectrophotometric method has been used to characterize water-soluble colloidal manganese dioxide obtained by the redox reaction between sodium thiosulphate and potassium permanganate in neutral aqueous medium which shows a single peak in the visible region with λmax = 425 nm. The kinetics of the oxidation of lactic acid by colloidal manganese dioxide (oxidant) has been investigated spectrophotometrically under pseudo-first-order conditions of excess lactic acid. The rate of the noncatalytic reaction pathway was slow which increased with increasing lactic acid concentration. The reaction was first-order with respect to [oxidant] as well as [lactic acid]. In presence of manganase(II) and fluoride ions, the noncatalytic path disappeared completely while the oxidation rate of autocatalytic path increased and decreased, respectively with increasing [Mn(II)] and [F-]. A mechanistic scheme in conformity with the observed kinetics has been proposed with the rate-law: v = -d[MnO2]/dt = κ1κ2[MnO2] [H+][lactic acid]T/ ([H+] Ka)(κ_1 + ≤2)
Characterization of two isotypes of l-threonine dehydratase from Entamoeba histolytica
Husain, Afzal,Jeelani, Ghulam,Sato, Dan,Ali, Vahab,Nozaki, Tomoyoshi
, p. 100 - 104 (2010)
The genome sequence of the enteric protozoan parasite Entamoeba histolytica suggests that amino acid catabolism plays an important role in energy metabolism. In the present study, we described kinetic and regulatory properties of catabolic l-threonine and l-serine dehydratase (TD) from E. histolytica. TD catalyses the pyridoxal phosphate-dependent dehydrative deamination of l-threonine and l-serine to ammonia and keto acids (2-oxobutyrate and pyruvate, respectively). E. histolytica possesses two TD isotypes (EhTD1-2) showing 38% mutual identity, a calculated molecular mass of 45.0 or 46.5 kDa, and an isoelectric point of 6.68 or 5.88, respectively. Only EhTD1 showed l-threonine and l-serine dehydrative deaminating activities whereas EhTD2, in which the amino acid residues involved in the substrate and cofactor binding were not conserved, was devoid of these activities. The kcat/Km value of EhTD1 was >3 fold higher for l-threonine than l-serine. EhTD1 was inhibited by l-cysteine in a competitive manner with the Ki values of 1.1 mM and 2.2 mM for l-serine and l-threonine, respectively. EhTD1 was insensitive to the allosteric activation by AMP or CMP. Three major substitutions of EhTD1 likely attribute to the insensitivity. EhTD1 was also inhibited about 50% by 20 mM 2-oxobutyrate, pyruvate, and glyoxylate; the inhibition was not, however, reversed by AMP. Together, these data showed that EhTD1 possesses unique regulatory properties distinct from other organisms and may play an important role in energy metabolism via amino acid degradation in E. histolytica.
A Convenient Electrochemical Synthesis of α-Oxoacids
Pokhodenko, Vitaly D.,Koshechko, Vjacheslav G.,Titov, Vladimir E.,Lopushanskaja, Victorija A.
, p. 3277 - 3278 (1995)
The possibility of obtaining aliphatic and aromatic-α-oxoacids via the direct electrochemical carboxylation of acetyl and benzoyl chlorides has been shown for the first time.
Kinetics and mechanism of the oxidation of some α-hydroxy acids by 2,2′-bipyridinium chlorochromate
Kumbhat, Vinita,Sharma, Pradeep K.,Banerji, Kalyan K.
, p. 248 - 254 (2002)
The oxidation of glycolic, lactic, malic, and a few substituted mandelic acids by 2,2′-bipyridinium chlorochromate (BPCC) in dimethylsulphoxide leads to the formation of corresponding oxoacids. The reaction is first order each in BPCC and the hydroxy acids. The reaction is catalyzed by the hydrogen ions. The hydrogen ion dependence has the form: kobs = a + b [H+]. The oxidation of α-deuteriomandelic acid exhibited a substantial primary kinetic isotope effect (kH/kd = 5.29 at 303 K). Oxidation of p-methylmandelic acid was studied in 19 different organic solvents. The solvent effect has been analyzed by using Kamlet's and Swain's multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed.
