- Chemical transformations of the condensation products of pyridoxal with L-α-alanine and D-α-alanine
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The kinetics and mechanism of the reactions of pyridoxal with L- and D-α-alanine were studied. Under comparable conditions, the condensation of L- and D-α-alanines with pyridoxal includes three kinetically different steps. The first fast step is addition
- Pishchugin,Tuleberdiev
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- The Ala95-to-Gly substitution in Aerococcus viridans l -lactate oxidase revisited - Structural consequences at the catalytic site and effect on reactivity with O2 and other electron acceptors
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Aerococcus viridansl-lactate oxidase (avLOX) is a biotechnologically important flavoenzyme that catalyzes the conversion of l-lactate and O2 into pyruvate and H2O2. The enzymatic reaction underlies different biosensor applications of avLOX for blood l-lactate determination. The ability of avLOX to replace O2 with other electron acceptors such as 2,6-dichlorophenol-indophenol (DCIP) allows the possiblity of analytical and practical applications. The A95G variant of avLOX was previously shown to exhibit lowered reactivity with O2 compared to wild-type enzyme and therefore was employed in a detailed investigation with respect to the specificity for different electron acceptor substrates. From stopped-flow experiments performed at 20 °C (pH 6.5), we determined that the A95G variant (fully reduced by l-lactate) was approximately three-fold more reactive towards DCIP (1.0 ± 0.1 × 106 M-1·s-1) than O2, whereas avLOX wild-type under the same conditions was 14-fold more reactive towards O2 (1.8 ± 0.1 × 106 m-1·s-1) than DCIP. Substituted 1,4-benzoquinones were up to five-fold better electron acceptors for reaction with l-lactate-reduced A95G variant than wild-type. A 1.65-? crystal structure of oxidized A95G variant bound with pyruvate was determined and revealed that the steric volume created by removal of the methyl side chain of Ala95 and a slight additional shift in the main chain at position Gly95 together enable the accomodation of a new active-site water molecule within hydrogen-bond distance to the N5 of the FMN cofactor. The increased steric volume available in the active site allows the A95G variant to exhibit a similar trend with the related glycolate oxidase in electron acceptor substrate specificities, despite the latter containing an alanine at the analogous position.
- Stoisser, Thomas,Rainer, Daniela,Leitgeb, Stefan,Wilson, David K.,Nidetzky, Bernd
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- Comparison of two metal-dependent pyruvate aldolases related by convergent evolution: Substrate specificity, kinetic mechanism, and substrate channeling
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HpaI and BphI are two pyruvate class II aldolases found in aromatic meta-cleavage degradation pathways that catalyze similar reactions but are not related in sequence. Steady-state kinetic analysis of the aldol addition reactions and product inhibition assays showed that HpaI exhibits a rapid equilibrium random order mechanism while BphI exhibits a compulsory order mechanism, with pyruvate binding first. Both aldolases are able to utilize aldehyde acceptors two to five carbons in length; however, HpaI showed broader specificity and had a preference for aldehydes containing longer linear alkyl chains or C2-OH substitutions. Both enzymes were able to bind 2-keto acids larger than pyruvate, but only HpaI was able to utilize both pyruvate and 2-ketobutanoate as carbonyl donors in the aldol addition reaction. HpaI lacks stereospecific control producing racemic mixtures of 4-hydroxy-2-oxopentanoate (HOPA) from pyruvate and acetaldehyde while BphI synthesizes only (4S)-HOPA. BphI is also able to utilize acetaldehyde produced by the reduction of acetyl-CoA catalyzed by the associated aldehyde dehydrogenase, BphJ. This aldehyde was directly channeled from the dehydrogenase to the aldolase active sites, with an efficiency of 84%. Furthermore, the BphJ reductive deacylation reaction increased 4-fold when BphI was catalyzing the aldol addition reaction. Therefore, the BphI-BphJ enzyme complex exhibits unique bidirectionality in substrate channeling and allosteric activation.
- Wang, Weijun,Baker, Perrin,Seah, Stephen Y. K.
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- Alcohol oxidation catalysed by Ru(VI) in the presence of alkaline hexacyanoferrate(III)
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The oxidation of sodium lactate, 2-methyl-2,4-pentanediol, 2,4-butanediol, 2-butanol and 2-propanol upon treatment with alkaline hexacyanoferrate(III) using a Ru(VI) catalyst is highly effective for the oxidation of alcohols by Fe(CN)63-. The reaction mechanism proposed involves the oxidation of the alcohol by the catalyst, a process that occurs through the formation of a substrate-catalyst complex. The decomposition of this complex yields Ru(IV) and a carbocation (owing to a hydride transfer from the α-C-H bond of the alcohol to the oxoligand of ruthenium). The role of the co-oxidant, hexacyanoferrate(III), is to regenerate the catalyst. In the oxidation reactions, the rate constants for complex decomposition and catalyst regeneration have been determined and a comparative study of the structure versus reactivity has been carried out. Copyright
- Poblete, Francisco J.,Corrochano, Pablo
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- A comparative study of the enolization of pyruvate and the reversible dehydration of pyruvate hydrate
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The enolization of pyruvate and the reversible dehydration of pyruvate hydrate were studied at 25.0°C using spectrophotometric methods. The enolization of pyruvate was followed at 353 nm by monitoring the rate of uptake of triiodide ion. The dehydration of pyruvate hydrate was initiated by introducing small quantities of preacidified solutions of pyruvic acid containing, at the kinetic zero, ca. 60% of the hydrate into buffer solutions. A decrease in absorbance at 325 nm took place as the reaction progressed to a final solution composition of 6% hydrate. The reactions were studied in acetate, MES, phosphate, arsenate, imidazole, 1-methylimidazole, HEPES, Tris, and borate buffers. The dehydration of pyruvate hydrate was found to be sensitive toward general-acid and general-base catalysis, while the enolization of pyruvate was catalyzed only by the basic components of the buffers studied. The corresponding rate coefficients were determined for the acidic and basic catalysts, and taking into account the appropriate statistical correction factors associated with the capacity of the catalysts to donate and accept protons, Br?nsted plots were constructed. Br?nsted coefficients were determined for enolization (β = 0.47) and for dehydration (α = 0.54, β= 0.52). While relatively normal catalytic behavior was observed for the enolization of pyruvate, deviations for the dehydration of hydrated pyruvate were noted. Analysis of these deviations, in light of a comparison of the relative magnitude of the catalytic rate coefficients for the reversible hydrations of other carbonyl compounds, suggests the possible contribution of a general-base catalytic path involving the intramolecular participation of the carboxylate group of hydrated pyruvate. The data are also considered in terms of the possible roles the rates of interconversion and positions of equilibria between keto, enol, and hydrated species may play in the physiological reactions of pyruvate. Finally, the Br?nsted analysis provides the necessary basis for a comparison of the relative susceptibilities of the many substrates of carbonic anhydrase II including pyruvate hydrate.
- Damitio,Smith,Meany,Pocker
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- Preparation method of sodium pyruvate
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The invention relates to the field of preparation of sodium pyruvate, in particular to a preparation method of sodium pyruvate. The preparation method comprises the following steps that ethyl lactateis subjected to an oxidizing reaction under existing of a catalyst, and sodium pyruvate is obtained after hydrolyzation and neutralization are conducted, wherein the catalyst is one or more of 2,2,6,6-tetramethylpiperidine oxide, 9-azabicyclo[3.3.1]nonane-N-oxy-compound, 9-azabicyclo[3.3.1]nonane-3-ene-N-oxy-compound, 4,2,2,6,6-tetrametylpiperidine oxide and 4-amino-2,2,6,6-tetrametylpiperidine oxide. Compared with the existing commonly used bromine, the prepared method of sodium pyruvate improves the reaction rate of oxidization, and in the oxidization reaction process, the reaction is more steady and safer. In addition, a by-product, namely yellow oily matter is reduced, and post-treatment is easier as well.
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Paragraph 0033-0122
(2018/07/30)
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- Discovery and characterization of a thermostable D-lactate dehydrogenase from Lactobacillus jensenii through genome mining
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The demand on thermostable D-lactate dehydrogenases (d-LDH) has been increased for d-lactic acid production but thermostable d-DLHs with industrially applicable activity were not much explored. To identify a thermostable d-LDH, three d-LDHs from different Lactobacillus jensenii strains were screened by genome mining and then expressed in Escherichia coli. One of the three d-LDHs (d-LDH3) exhibited higher optimal reaction temperature (50 °C) than the others. The T5010 value of this thermostable d-LDH3 was 48.3 °C, much higher than the T5010 values of the others (42.7 and 42.9 °C) and that of a commercial D-lactate dehydrogenase (41.2 °C). The Tm values were 48.6, 45.7 and 55.7 °C for the three d-LDHs, respectively. In addition, kinetic parameter (k cat/Km) of d-LDH3 for pyruvate reduction was estimated to be almost 150 times higher than that for lactate oxidation at pH 8.0 and 25 °C, implying that D-lactate production from pyruvate is highly favored. These superior thermal and kinetic features would make the d-LDH3 characterized in this study a good candidate for the microbial production of D-lactate at high temperature from glucose if it is genetically introduced to lactate producing microbial.
- Jun, Chanha,Sa, Young Seung,Gu, Sol-A,Joo, Jeong Chan,Kim, Seil,Kim, Kyung-Jin,Kim, Yong Hwan
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p. 109 - 117
(2013/04/10)
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- Rational design of stereoselectivity in the class II pyruvate aldolase BphI
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BphI, a pyruvate-specific class II aldolase, catalyzes the reversible carbon-carbon bond formation of 4-hydroxy-2-oxoacids up to eight carbons in length. During the aldol addition catalyzed by BphI, the S-configured stereogenic center at C4 is created via attack of a pyruvate enolate intermediate on the si face of the aldehyde carbonyl of acetaldehyde to form 4(S)-hydroxy-2-oxopentanoate. Replacement of a Leu-87 residue within the active site of the enzyme with polar asparagine and bulky tryptophan led to enzymes with no detectable aldolase activity. These variants retained decarboxylase activity for the smaller oxaloacetate substrate, which is not inhibited by excess 4-hydroxy-2-oxopentanoate, confirming the results from molecular modeling that Leu-87 interacts with the C4-methyl of 4(S)-hydroxy-2-oxoacids. Double variants L87N;Y290F and L87W;Y290F were constructed to enable the binding of 4(R)-hydroxy-2-oxoacids by relieving the steric hindrance between the 5-methyl group of these compounds and the hydroxyl substituent on the phenyl ring of Tyr-290. The resultant enzymes were shown to exclusively utilize only 4(R)- and not 4(S)-hydroxy-2-oxopentanoate as the substrate. Polarimetric analysis confirmed that the double variants are able to synthesize 4-hydroxy-2-oxoacids up to eight carbons in length, which were the opposite stereoisomer compared to those produced by the wild-type enzyme. Overall the kcat/K m values for pyruvate and aldehydes in the aldol addition reactions were affected 10-fold in the double variants relative to the wild-type enzyme. Thus, stereocomplementary class II pyruvate aldolases are now available to create chiral 4-hydroxy-2-oxoacid skeletons as synthons for organic reactions.
- Baker, Perrin,Seah, Stephen Y. K.
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scheme or table
p. 507 - 513
(2012/03/07)
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- A rationally designed aldolase foldamer
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(Chemical Equation Presented) Neatly folded: A decameric β-peptide shows enzyme-like catalytic properties. The foldamer, which bears a terminal heptanoyl unit and displays a thermostable helical structure with an array of ammonium-group side chains, accel
- Mueller, Manuel M.,Windsor, Matthew A.,Pomerantz, William C.,Gellman, Samuel H.,Hilvert, Donald
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supporting information; experimental part
p. 922 - 925
(2009/05/15)
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- DIALYSIS SOLUTIONS CONTAINING PYROPHOSPHATES
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Dialysis solutions comprising pyrophosphates and methods of making and using the dialysis solutions are provided. In an embodiment, the present disclosure provides a dialysis solution comprising a stable and therapeutically effective amount of pyrophosphate. The dialysis solution can be sterilized, for example, using a technique such as autoclave, steam, high pressure, ultra-violet, filtration or combination thereof. The dialysis solution can be in the form of a concentrate.
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- METHOD FOR THE PRODUCTION OF ALPHA-KETO ACIDS AND ESTERS THEREOF
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The invention relates to a method for the production of a-keto acids and esters thereof, in particular to a method of producing13C1-α-keto acids and esters thereof i.e. α-keto acids and esters thereof which are 13C-enriched at the C1-atom (carboxyl atom). More particularly, the invention relates to a method of producing pyruvic acid and esters thereof, in particular 13C1-pyruvic acid and esters thereof.
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(2008/12/05)
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- Enzymatic generation and in situ screening of a dynamic combinatorial library of sialic acid analogues
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Reversible formation of carbon-carbon bonds under physiological conditions by enzyme catalysis allows the generation and in situ screening of a dynamic mixture of biologically significant compounds. Generation of the dynamic library by incubation of the three sugars 1 a-c with two equivalents of sodium pyruvate in the presence of N-acetylneuraminic acid aldolase and wheat germ agglutinin resulted in amplification of sialic acid 1a (see scheme).
- Lins, Roger J.,Flitsch, Sabine L.,Turner, Nicholas J.,Irving, Ed,Brown, Stuart A.
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p. 3405 - 3407
(2007/10/03)
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- Method for producing alkali metal and alkaline earth metal pyruvates
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A method for producing alkali metal and alkaline earth metal pyruvates is disclosed, in which salts of organic acids or acidic organic keto or hydroxy compounds containing as cation one from the group comprising Li, Na, K, Rb, Cs, Mg, Sr and Ba, or mixtures of these salts, are reacted with pyruvic acid at a temperature ranging from ?20 to +120°C., if necessary in the presence of a solvent or diluent. In this way, alkali metal and alkaline earth metal pyruvates of high purity are obtained, which can be largely anhydrous and have a very long shelf life. In addition, novel Rb, Cs, Sr and Ba pyruvates are disclosed. These pyruvates are used, for example, to enhance endurance and strength in the field of sport, as protective substances for body cells and tissues, and as food supplements. They are also used for technical applications.
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- Means and method for the prevention and or treatment of trypanosomosis
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The invention provides means and methods for obtaining a factor capable of at least in part inducing growth arrest and/or cell death of a trypanosome. Means of the invention include one or more factors that may be purified from culture medium of a culture of trypanosomes, or may be synthesised chemically or produced in a biotechnological process. The invention provides methods for the preparation of medicines for the treatment of Trypanosomosis. The invention further provides vaccines and methods for the preparation of vaccines for the treatment of Trypanosomosis.
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- The reversible enolization and hydration of pyruvate: Possible roles of keto, enol, and hydrated pyruvate in lactate dehydrogenase catalysis
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The reversible enolization and hydration of pyruvic acid and pyruvate anion were monitored using spectrophotometric methods at several temperatures. Widely varying values for the equilibrium constant for the enolization of pyruvic acid and pyruvate ion appear in the literature. To accurately determine the position of equilibrium for the enolization reaction, we have developed a method that gives consistent results in which purified samples of sodium pyruvate are first "titrated" with triiodide ion to remove any triiodide-scavenging impurities such as those resulting from aldol condensation reactions. After reequilibration to allow the regeneration of enol pyruvate, the addition of small quantities of triiodide result in an initial burst in the decrease of absorbance at 353 nm, followed by the much slower zero-order decrease due to the formation of new enol pyvuvate molecules. The absorbance change during the burst phase of the reaction is proportional to the enol concentration plus that of any triiodide-scavenging impurity which may be present in the original pyruvate solution. Thus, as the quantity of triiodide used in the pretreatment stage of the experiments is increased, these burst absorbance changes, ΔA, decrease until a constant value of ΔA is reached. Accordingly, this final ΔA value is proportional to enol pyruvate (or enol pyruvic acid) in the absence of triiodide-scavenging impurity, allowing the accurate and reproducible determinations of Kenol. The equilibrium constants for both pyruvate and pyruvic acid are relatively temperature insensitive and, typically, Kenol (pyruvate anion) = 2.6 × 10-5 and Kenol (pyruvic acid) = 7.8 × 10-5 at 25.0°C. The zero-order phase of the reaction of triiodide ion may be used to calculate rate constants for enolization. The hydration and dehydration of pyruvic acid were followed directly by following absorbance changes in the peak at 340 nm due to the keto group. The thermodynamic and kinetic results reported in this paper are used to help determine whether the observed "substrate" inhibition of the lactate dehydrogenase catalyzed reduction of pyruvate is actually caused by keto, hydrated, or enol pyruvate.
- Esposito,Lukas,Meany,Pocker
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p. 1108 - 1117
(2007/10/03)
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- Oxydation catalytique du lactate en pyruvate sur electrode de platine modifiee par des ad-atomes de plomb
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Catalytic oxidation of lactate into pyruvate on a platinum electrode modified by lead ad-atoms.The effects of underpotentially deposited Pb on the oxidation of sodium lactate at a Pt electrode was studied by recording cyclic voltammograms.The activity of the modified electrode towards the electro-oxidation of sodium lactate in alkaline solution was found to be higher than that of bulk platinum.A deactivation of the electrocatalyst was observed when the pyruvate concentration was high, suggesting its preferential adsorption on the catalyst. - Keywords: cyclic voltammetry / modified electrode / catalysis / lead ad-atoms / electrocatalysis / lactate oxidation / pyruvate
- Lyazidi, Hamida Ait,Boukhedena, Mohamed,Mestre, Muriel,Fauvarque, Jean-Francois
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p. 1039 - 1046
(2007/10/02)
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- Process for preparing pyruvate
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A process for preparing pyruvate in high yield is disclosed, comprising reacting propylene glycol with molecular oxygen in an aqueous solution in the presence of a platinum catalyst containing a metallic component selected from the group consisting of lead, thallium, and cadmium while controlling the pH of the reaction mixture between 7 and 9. The crude pyruvate can be purified by treating with activated carbon in the presence of water.
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- Synthesis and Hydrolysis Studies of Phosphonopyruvate
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Phosphonopyruvate (1) is prepared in 56percent yield from triethyl phosphonopyruvate (3) and pKa values of 1.63, 2.40 and 7.41 determined.The stability of phosphonopyruvate is monitored at 75 deg C in aqueous buffers over pH range 0.6 to 8.3.The only products detected are pyruvate and inorganic phosphate.The pH-rate profile shows that the C-P bond is hydrolysed fastest in the monoanion and dianion of phosphonopyruvate, with rate constants of 1.94 * 10-4 s-1 for the monoanion and 1.05 * 10-4 s-1 for the dianion.For the reaction at pH 4.75, where the dianion predominates, ΔH(excit.) is 114.0 kJ mol-1 and ΔS(excit.) is 5.4 J mol-1 K-1, the deuterium isotope effect, kH/kD is 1.08 +/- 0.04, and there is non-selective phosphorylation of methanol and H2O in an equimolar solution of these solvents.These results are consistent with a mechanism of hydrolysis of both the monoanion and dianion that involves a very largely dissociative transition state with monomeric metaphosphate character.
- Freeman, Sally,Irwin, William J.,Schwalbe, Carl H.
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p. 263 - 267
(2007/10/02)
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- Tumor cell growth-inhibiting pharmaceutical compositions containing phosphino-hydrocarbon-gold, silver or copper complexes
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Pharmaceutical compositions and a method for inhibiting the growth of tumor cells by administering a tumor cell growth-inhibiting amount of a bis[bis (diphenylphosphino)hydrocarbon]-, bis[bis(diethylphsophino) hydrocarbon]-, bis[bis(diphenylphosphine-deithylphosphino) hydrocarbon]gold(I), silver(I) or copper(I) complex or a tris[bis(diphenylphosphino)ethane] dicopper(I) complex to an animal afflicted with said tumor cells.
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- Functinalised Bilayer Vesicle as a Catalyst for Transamination: Artificial Transaminase
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The non-enzymatic transamination reaction of α-amino acids with α-keto acids was investigated in aqueous media at 30 deg C.The functionalised single-walled co-vesicle composed of a synthetic peptide lipid, N,N-dihexadecyl-Nα--L-histidinamide bromide, and a hydrophobic pyridoxal derivative, 1-(NN-dihexadecylcarbamoylmethyl)-2-methyl-3-hydroxy-4-formyl-5-hydroxymethylpyridinium chloride, effectively catalysed amino-group transfer from L-phenylalanine to pyruvic acid in the presence of copper(II) ions, showing turnover behaviour. the catalytic activity of the vesiculer system was much higher than those of 1,2-dimethyl-3-hydroxy-4-formyl-5-hydroxymethyl-pyridinium chloride and pyridoxal examined in aqueous media containing copper(II ions.The rate-determining step involved in the catalytic cycle performed with the vesicular catalyst is primarily assigned to the product-releasing process, the hydrolysis of the copper(II) chelate of the aldimine Schiff's base to afford alanine.
- Murakami, Yukito,Kikuchi, Jun-ichi,Akiyoshi, Kazunari,Imori, Toru
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p. 1919 - 1924
(2007/10/02)
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