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PubMed1989

Branched-chain alpha-ketoacids and related acids in thiamin-deprived rats.

We showed elevated plasma levels of branched-chain amino acids, alpha-ketoacids, alpha-hydroxyacids in thiamin-deprived rats, which had decreased liver thiamin levels (2.4% of control) after 4 weeks of feeding of thiamin-deficient diet. The ratios of mean levels of these acids in thiamin-deficient rats to those in control rats were as follows: total branched-chain amino acids 1.6; total branched-chain alpha-ketoacids 2.7; total branched-chain alpha-hydroxyacids 3.6; pyruvic acid 1.6. The plasma level of total branched-chain alpha-hydroxyacids was correlated to liver thiamin concentration (r = -0.67, p less than 0.01), but those of the other two acids were not correlated. Although the increased levels of branched-chain acids in thiamin-deprived rats were less remarkable than those of ill patients with maple syrup urine disease, they reflect the reportedly decreased branched-chain alpha-ketoacid dehydrogenase activities (about 40% of control), and we discussed whether the toxic effects of individual branched-chain acid could be demonstrated by its administration to the thiamin-deprived rats.

Amino Acids, Branched-Chain↗
PubMedDate not supplied

[Amination and biosynthesis of glutamate by R- and S-forms of Bacillus thuringiensis].

These studies were designed to determine the biochemical nature of the Bacillus thuringiensis growth being dependent on glutamate during cultivation in a minimal medium. This is possible to be due to the absence of enzymes which catalyze glutamic acid synthesis by direct amination of alpha-ketoglutaric acid, glutamate dehydrogenase and glutamate synthase, and a decrease in the activity of the enzyme catalyzing amination of pyruvic acid, alanine dehydrogenase. It has been shown that the lack of glutamate can be compensated by histidine and proline; in this case, the growth efficiency of R form is greater than that of S form which is consistent with an increased rate of protein synthesis of R form.

Alanine↗
PubMedDate not supplied

Mutagenic investigation of flavourings: dimethyl succinate, ethyl pyruvate and aconitic acid are negative in the Salmonella/mammalian-microsome test.

Three flavourings: dimethyl succinate, ethyl pyruvate and aconitic acid, commonly used in candy, beverages, and baked goods, were tested in the Salmonella/mammalian-microsome test. Tester strains were TA 1535, TA 100, TA 1537 and TA 98 and doses were 32, 160, 800, 4000 and 20 000 micrograms per plate. All tests were performed with and without the S9 fraction from Aroclor induced rat liver. None of the flavourings showed mutagenic potential. These results support the classification made by the Council of Europe, List I (1981).

Aconitic Acid↗
PubMed1983

Effect of pyridoxine alpha-ketoglutarate (PAK) on ammonia and pyruvic and lactic acid blood levels in patients with cirrhosis.

Administration of PAK to patients with hepatic cirrhosis significantly reduced hyperammonaemia and plasma levels of pyruvic and lactic acid. No significant changes in glycaemia were found. PAK treatment increased plasma levels of glutamic acid and decreased plasma levels of glutamine. This double-blind placebo controlled trial showed that PAK administration has a positive effect on some metabolic disturbances in cirrhotic patients.

Aged↗
PubMed1987

Biotransformation of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-1-carboxylic acid to harmalan, tetrahydroharman and harman in rats.

1-Methyl-1,2,3,4-tetrahydro-beta-carboline-1-carboxylic acid (1-carboxytetrahydroharman, 1-CTHH) has been detected in the brain of rats following intracerebroventricular injection of tryptamine and pyruvic acid. We now report the metabolism of this compound. Following intraperitoneal injection of 1-CTHH into rats, harmalan was found to be the major metabolite besides tetrahydroharman (THH) and harman. A high concentration of THH was measured in the lung while most of harman was found in the urine. Harmalan and THH could be detected in the brain in low concentrations. The products were separated following extraction from tissues by high-performance liquid chromatography (HPLC) on a reversed phase C18-DB column. The identity of the metabolites was confirmed by mass spectrometry (MS) analysis. The results demonstrate the role of 1-CTHH as a precursor of the biologically active compounds harmalan, THH and harman.

Animals↗
PubMed2005

Updated knowledge about the presence of phenolic compounds in wine.

Phenolic compounds are partly responsible for the color, astringency, and bitterness of wine, as well as for numerous physiological properties associated with wine consumption. Mass spectrometry has allowed for great progress in the identification and characterization of wine polyphenols. The aim of the present article is to summarize the numerous advances recently achieved in this field. The main type of phenolic compounds found in wine, including hydroxybenzoic and hydroxycinnamic acids, stilbenes, flavones, flavonols, flavanonols, flavanols, and anthocyanins, are firstly described. Chemical reactions and mechanisms involving phenolic compounds during winemaking are also extensively discussed, including enzymatic and chemical oxidation reactions, direct and acetaldehyde-mediated anthocyanin-tannin condensation reactions, acetaldehydemediated and glyoxylic acid-mediated tannin-tannin condensation reactions and, C-4/C-5 anthocyanin cycloaddition reactions with 4-vinylphenols, vinylflavanols and pyruvic acid, among others, leading to the formation of pyranoanthocyanins. Useful mass spectral data of well-known and novel phenolic compounds recently identified in wine, and details related to their fragmentation pathway according to different ionization techniques, are given.

Anthocyanins↗
PubMed1991

Molecular cloning of the gene for indolepyruvate decarboxylase from Enterobacter cloacae.

Although indole-3-acetic acid (IAA) is a well-known plant hormone, the main IAA biosynthetic pathway from L-tryptophan (Trp) via indole-3-pyruvic acid (IPyA) has yet to be elucidated. Previous studies have suggested that IAA is produced by Enterobacter cloacae isolated from the rhizosphere of cucumbers and its biosynthetic pathway may possibly be the same as that in plants. To elucidate this pathway, the IAA biosynthetic gene was isolated from a genomic library of E. cloacae by assaying for the ability to convert Trp to IAA. DNA sequence analysis showed that this gene codes for only one enzyme and its predicted protein sequence has extensive homology with pyruvate decarboxylase in yeast and Zymomonas mobilis. Cell-free extracts prepared from Escherichia coli harboring this gene could convert IPyA to indole-3-acetaldehyde (IAAld). These results clearly show that this pathway is mediated only by indolepyruvate decarboxylase, which catalyzes the conversion of IPyA to IAAld.

Amino Acid Sequence↗
PubMed1979

Regulation of the G1 leads to S phase transition in chick embryo fibroblasts with alpha-keto acids and L-alanine.

Temporal inhibition of protein synthesis with cycloheximide prevents subsequent insulin, but not serum-stimulated DNA synthesis in G1-arrested chick embryo fibroblasts (CEF). The inhibition is measured by the incorporation of 3H-thymidine into acid insoluble material and confirmed by chemical estimate of the DNA content of inhibited and uninhibited cells. Cycloheximide treatment is without effect if the cell cultures are maintained at 4 degrees C while exposed to the drug. Several alpha-keto acids (pyruvate, oxaloacetate, alpha-ketobutyrate) at 0.5-1 mM concentrations restore DNA synthesis in previously inhibited cells when combined with insulin. L-alanine (D-alanine is inert) is even more effective than the keto acids in stimulating DNA synthesis after cycloheximide treatment. Glucose transport was unaffected by cycloheximide treatment while lactate levels in medium from inhibited, insulin-stimulated CEF were reduced 70% compared to uninhibited counterparts. We speculate that cycloheximide treatment may lead to the decay of a glycolytic enzyme which compromises the ability of inhibited cells to synthesize pyruvate from glucose, and thus induces an exogenous requirement for alpha-keto acid or L-alanine. A serum component(s) with a molecular weight of about 100 permitted insulin-stimulated DNA synthesis in inhibited cells.

Alanine↗
PubMed1977

Further potential sources of energy modifying the multiplication of Mycobacterium leprae.

The multiplication of Mycobacterium leprae was modified by graded dilutions of organic acids. 0.01%-0.05% gluconic acid inhibited its multiplication. 0.005% of it promoted the growth of 2 out of 6 strains. 0.2% - 1.0% glucuronic acid promoted the multiplication of the majority of strains. 2.0% inhibited their multiplication, and 0.05% promoted the growth of one strain. Galacturonic and pyruvic acids were active in 0.2 - 2.0% concentrations, while the activity of citric acid was mainly noted at 1.0 and 2.0% concentrations.

Cell Differentiation↗
PubMedDate not supplied

Cerebrospinal fluid and arterial lactate, pyruvate and acid-base balance in patients with intracranial hemorrhages.

Lactate and pyruvate concentrations and acid-base balance in cerebrospinal fluid (CSF) and arterial blood were determined in patients with intracranial hemorrhages (28 subarachnoid hemorrhages and 15 intracerebral hemorrhages). A greater increase in CSF lactate and lactate-pyruvate ratio (L/P ratio) was observed in patients with impairment of consciousness, focal neurological deficits, poor prognosis, or CSF pressures higher than 300 mm H2O. A combination of CSF lactate greater than 2.5 mM per liter, L/P ration above 20, bicarbonate less than 20.4 mEq per liter, pH below 7.276, or arterial PCO2 below 31.5 mm Hg seems to indicate poor prognosis from intracranial hemorrhage. The mechanism of hyperventilation in acute cerebrovascular diseases and of CSF pH regulation in acid-base disturbances was also discussed.

Acid-Base Imbalance↗
PubMed2003

Purification, characterization, and molecular cloning of a novel amine:pyruvate transaminase from Vibrio fluvialis JS17.

A transaminase from Vibrio fluvialis JS17 showing activity toward chiral amines was purified to homogeneity and its enzymatic properties were characterized. The transaminase showed an apparent molecular mass of 100 kDa as determined by gel filtration chromatography and a subunit mass of 50 kDa by MALDI-TOF mass spectrometry, suggesting a dimeric structure. The enzyme had an isoelectric point of 5.4 and its absorption spectrum exhibited maxima at 320 and 405 nm. The optimal pH and temperature for enzyme activity were 9.2 and 37 degrees C, respectively. Pyruvate and pyridoxal 5'-phosphate increased enzyme stability whereas (S)-alpha-methylbenzylamine reversibly inactivated the enzyme. The transaminase gene was cloned from a V. fluvialis JS17 genomic library. The deduced amino acid sequence (453 residues) showed significant homology with omega-amino acid:pyruvate transaminases (omega-APT) from various bacterial strains (80 identical residues with four omega-APTs). However, of 159 conserved residues in the four omega-APTs, 79 were not conserved in the transaminase from V. fluvialis JS17. Taken together with the sequence homology results, and the lack of activity toward beta-alanine (a typical amino donor for the omega-APT), the results suggest that the transaminase is a novel amine:pyruvate transaminase that has not been reported to date.

Amino Acid Sequence↗
PubMed2004

Chemical conversion of alpha-keto acids in relation to flavor formation in fermented foods.

Formation of flavor compounds from branched-chain alpha-keto acids in fermented foods such as cheese is believed to be mainly an enzymatic process, while the conversion of phenyl pyruvic acid, which is derived from phenylalanine, also proceeds chemically. In this research, the chemical conversion of alpha-keto acids to aldehydes with strong flavor characteristics was studied, with the main focus on the conversion of alpha-ketoisocaproic acid to the aldehyde 2-methylpropanal, and a manganese-catalyzed reaction mechanism is proposed for this conversion. The mechanism involves keto-enol tautomerism, enabling molecular oxygen to react with the beta-carbon atom of the alpha-keto acid, resulting in a peroxide. This peroxide can react in several ways, leading to unstable dioxylactone or noncyclic intermediates. These intermediates will break down into an aldehyde and oxalate or carbon oxides (CO and CO(2)). All the alpha-keto acids tested were converted at pH 5.5 and in the presence of manganese, although their conversion rates were rather diverse. This chemical reaction might provide new ways for controlling cheese flavor formation with the aim of acceleration of the ripening process or diversification of the flavor characteristics.

Aldehydes↗
PubMed1982

Novel formation of alpha-amino acids and their derivatives from oxo acids and ammonia in an aqueous medium.

In the course of a study of chemical evolution of the primeval sea, a novel reaction of carbonyl compounds with ammonia was found. Glyoxylic acid reacted with ammonia to afford N-oxalylglycine, which gave glycine in a 3-20% yield after 6 N HCl hydrolysis. Similarly, glyoxylic acid was treated with methylamine to give N-oxalylsarcosine, which afforded sarcosine in a 9-12% yield upon hydrolysis. Pyruvic acid reacted with ammonia to give N-acetylalanine, which gave alanine in a 1-4% yield upon hydrolysis. These reactions provide a novel and facile route to alpha-amino acids and their derivatives. A mechanism for the reactions is proposed.

Amino Acids↗
PubMed2001

Crystallization and initial X-ray diffraction analysis of human pyruvate dehydrogenase.

Human pyruvate dehydrogenase (E1) is a component enzyme of the pyruvate dehydrogenase complex. The enzyme catalyzes the irreversible decarboxylation of pyruvic acid and the rate-limiting reductive acetylation of the lipoyl moiety linked to the dihydrolipoamide acetyltransferase component of the pyruvate dehydrogenase complex. E1 is an alpha(2)beta(2) tetramer ( approximately 154 kDa). Crystals of this recombinant enzyme have been grown in polyethylene glycol 3350 using a vapor-diffusion method at 295 K. The crystals are characterized as orthorhombic, space group P2(1)2(1)2(1), with unit-cell parameters a = 64.2, b = 126.9, c = 190.2 A. Crystals diffracted to a minimum d spacing of 2.5 A. The asymmetric unit contains one alpha(2)beta(2) tetrameric E1 assembly; self-rotation function analysis showed a pseudo-twofold symmetry relating the two alphabeta dimers.

Crystallization↗
PubMed1989

Enhancement of growth of Mycobacterium malmoense by acidic pH and pyruvate.

The growth of Mycobacterium malmoense is dysgonic and slow on ordinary mycobacterium media. The effect of pH and pyruvate on the growth of ten strains was studied on a modification of Löwenstein-Jensen medium. Growth appeared sooner and was more abundant at pH less than 6.5. At pH 7 or higher, it was scarcely or not at all visible after six weeks of incubation. Pyruvate enhanced the growth of five strains that grew only poorly on glycerol-containing medium, even at acidic pH. The parallel use of both pyruvate and glycerol-containing media, pH 6 to 6.5, and an incubation period of seven weeks or longer are recommended for the isolation of Mycobacterium malmoense on Löwenstein-Jensen medium.

Culture Media↗
PubMed1976

The inhibition of insulin secretion from the perfused rat pancreas after thyroxine treatment.

Thyroxine treatment did not significantly affect the immediate insulin secretory response of the perfused rat pancreas, but it inhibited the late phase of D-glucose-induced insulin secretion. Thyroxine treatment did not inhibit D-glyceraldehyde-, D-mannose-, and tolbutamide-induced insulin release from the perfused pancreas. An increase in the D-glucose concentration of the perfusion medium as well as feeding of the rats did not restore insulin secretion after thyroxine treatment. The inhibition of D-glucose-induced insulin release in response to thyroxine treatment was reversed after addition of either D-glyceraldehyde, dihydroxyacetone, DL-glyceric acid, pyruvate, or alpha-ketobutyrate to the perfusion medium. Tolbutamide, L-glucose, D-fructose, D-mannose, L-lactate, and propionic acid were not able to overcome the inhibition of D-glucose-induced insulin secretion. Except for alpha-ketobutyrate all substances which were effective in reversing the inhibition of D-glucose-induced insulin release were glycolytic intermediates. Comparing the glycolytic alpha-ketoacid pyruvate and the non-glycolytic ketoacid alpha-ketobutyrate, the only part common to both substances was the ketoacid moiety. It is concluded from these findings that the ketoacid moiety of the alpha-ketoacids plays an important role in reversing the effect of thyroxine on D-glucose-induced insulin release.

Animals↗