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Quantitative analysis of hydralazine pyruvic acid hydrazone, the major plasma metabolite of hydralazine.

A specific, high-performance liquid chromatographic technique for the measurement of hydralazine pyruvic acid hydrazone is described. This method utilized reversed-phase chromatography for the separation of this hydrophilic metabolite of hydralazine from other fluid constituents present in serum, plasma, or urine of human volunteers and rabbits receiving hydralazine. Detection of the compound of interest is accomplished spectrophotometrically at 250 nm.

Animals↗

Evidence that the reaction of the UDP-N-acetylglucosamine 1-carboxyvinyltransferase proceeds through the O-phosphothioketal of pyruvic acid bound to Cys115 of the enzyme.

The enzyme UDP-N-acetylglucosamine 1-carboxyvinyltransferase (enolpyruvyltransferase, EC 2.5.1.7) catalyses the transfer of the intact 1-carboxyvinyl moiety of phosphoenolpyruvate to the 3'-hydroxyl group of the glucosamine moiety of UDP-(2')-N-acetylglucosamine with the concomitant release of inorganic phosphate, the first committed step in the biosynthesis of the bacterial cell wall peptidoglycan. Overexpression of the enzyme from Enterobacter cloacae in Escherichia coli allowed the isolation of large amounts of purified enzyme (approx. 900 mg/20 g fresh mass bacteria). By incubating the enzyme with 14C-labelled phosphoenolpyruvate, 32P-labelled orthophosphate and unlabelled UDP-(2')-N-acetyl-(3')-1-carboxyvinylglucosamine, we were able to isolate and characterise a reaction intermediate, covalently bound to the protein. It contains stoichiometric quantities of the C3 moiety (0.98 mol/mol) as well as of the phosphate moiety (0.95 mol/mol) of phosphoenolpyruvate relative to protein. The rapid turnover of this protein-bound intermediate in the presence of UDP-(2')-N-acetylglucosamine towards the product UDP-(2')-N-acetyl-(3')-1-carboxyvinylglucosamine suggests that the intermediate is kinetically competent. We also present evidence that the intermediate is bound as the O-phosphothioketal of pyruvic acid to Cys115 of the enzyme. This is the same Cys residue to which phosphomycin, an irreversible inhibitor of the UDP-GlcNAc carboxyvinyltransferase, binds covalently. Exchange of Cys115 for a Ser residue resulted in an inactive enzyme, demonstrating the essential role of Cys115 for the reaction. The only other enzyme known to catalyse the transfer of the intact 1-carboxyvinyl moiety of phosphoenolpyruvate to a substrate is the 3-phosphoshikimate 1-carboxyvinyltransferase (EC 2.5.1.19), the sixth enzyme of the shikimate pathway. The reaction of this synthase is known to proceed through a single, tightly but not covalently bound, tetrahedral intermediate. Even though the two enzymes share similarities in their primary amino acid sequences, their reaction mechanisms appear to be substantially different.

Alkyl and Aryl Transferases↗

[Carbohydrate and pyruvic acid degradation pathways in Fusidium coccineum strains with varying levels of antibiotic synthesis].

A number of enzymes and reactions of glycolysis, pentose-phosphate cycle and degradation of pyruvic acid in strains of F. coccineum with various levels of antibiotic production was studied comparatively. The experiments showed that highly productive strains were characterized by higher activity of the NADP-deficient enzymes of the pentoze-phosphate cycle as compared to the low active strains. The activity levels of glycolytic enzymes, such as fructose-diphosphate-aldolase and 3-phosphoglycerolaldehydehydrogenase did not practically differ. Significant differences were found in the reactions of puryvic acid degradation: the activity of cytoplasmic pyruvatedecarboxylase in the mutant with high antibiotic production level was lower than that in the low productive strain, while oxidation of the pyruvate of the mitochondrial fraction was on the contrary more intensive than in the highly productive strain. Therefore, metabilism in the strains studied was characterized by ever-increasing biochemical changes with an increase in their antibiotic productivity. Lowering of the growth rate of the mutants as their capacity for antibiotic supersynthesis increased and subsequently the anabolic processes became more intensive was accompanied by increasing derepression of the key enzymes of carbohydrate metabolism and in particular NADR-deficient dehydrogenase of the pentose cycle and pyruvatedehydrogenase, significant for fusidin biosynthesis and providing production of the antibiotic of steroid nature by cofactor NADP-H and acetyl-KoA, the primary precursor.

Anti-Bacterial Agents↗

Crystal structure analysis of omega-amino acid:pyruvate aminotransferase with a newly developed Weissenberg camera and an imaging plate using synchrotron radiation.

The three-dimensional structure of omega-amino acid:pyruvate aminotransferase from Pseudomonas sp. F-126, an isologous alpha 4 tetramer containing pyridoxal 5'-phosphate (PLP) as a cofactor, has been determined at 2.0 A resolution. The diffraction data were collected with a newly developed Weissenberg camera with a Fuji Imaging Plate, using synchrotron radiation. The mean figure-of-merit was 0.57. The subunit is rich in secondary structure and comprises two domains. PLP is located in the large domain. The high homology in the secondary structure between this enzyme and aspartate aminotransferase strongly indicates that these two types of enzymes have evolved from a common ancestor.

Aspartate Aminotransferases↗

Determination of indole-3-pyruvic acid levels in Arabidopsis thaliana by gas chromatography-selected ion monitoring-mass spectrometry.

A rapid and simple method is described for the determination of indole-3-pyruvic acid (IPA) levels in Arabidopsis thaliana by gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS). The method includes derivatization of IPA with hydroxylamine in the crude extract, followed by ethyl acetate partitioning, solid-phase extraction with C18 resin, reversed-phase high-performance liquid chromatography (HPLC), and GC-SIM-MS. Three derivatizing reagents were tested; these were pentafluorobenzylhydroxylamine, pentafluorophenylhydrazine, and hydroxylamine. Hydroxylamine proved to be the most useful, as the IPA-oxime was easiest to purify from plant extracts and was the most stable. IPA was quantified in Arabidopsis seedlings ranging in age from 5 to 12 days; levels varied from 4 to 13 ng/g, peaking at 7-9 days.

Arabidopsis↗

[Photochemical formation of pyruvic acid in a solution of acetaldehyde and ammonium nitrate].

It has been demonstrated that UV irradiation of acetaldehyde (2.5%) and ammonium nitrate (1.5%) solutions results in the synthesis of the pyruvic acid (PA). With the increase in the duration of irradiation, the yield of the produced PA decreases which is associated both with its photolysis and with its further transformations, for instance, into amino acids. The results obtained are discussed in relation to abiogenic synthesis of biologically important compounds in prebiological evolution and to possible development of metabolic pathways which are found in contemporary organisms.

Acetaldehyde↗