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PubMed1996

Effect of glucagon on the xylitol-induced increase in the plasma concentration and urinary excretion of purine bases.

To investigate whether glucagon affects the xylitol-induced increase in the production of purine bases (hypoxanthine, xanthine, and uric acid), the present study was performed with five healthy subjects. Intravenous administration of 300 mL 10% xylitol increased the plasma concentration and urinary excretion of purine bases, erythrocyte concentrations of adenosine monophosphate (AMP) and adenosine diphosphate (ADP), and blood concentrations of glyceraldehyde-3-phosphate (GA3P) + dihydroxyacetone phosphate (DHAP), fructose-1,6-bisphosphate (FBP), and lactic acid; it decreased the blood concentration of pyruvic acid and the plasma concentration and urinary excretion of inorganic phosphate. However, intravenous administration of 1 mg glucagon together with xylitol reduced the xylitol-induced changes in oxypurines, pyruvic acid, GABP + DHAP, and FBP, whereas it promoted the xylitol-induced increase in the urinary excretion of total purine bases and did not affect the xylitol-induced increase in the plasma concentration of total purine bases. In addition, in vitro study demonstrated that sodium pyruvate prevented the xylitol-induced degradation of adenine nucleotides in erythrocytes. These results suggested that gluconeogenesis due to glucagon increased the production of pyruvic acid, accelerated the conversion of NADH to NAD, and thereby prevented both the xylitol-induced degradation of adenine nucleotides in organs similar to erythrocytes and the inhibition of xanthine dehydrogenase in the liver and small intestine, resulting in decreases in the plasma concentration and urinary excretion of oxypurines. However, it was also suggested that in the liver storing glycogen, glucagon-induced glycogenolysis accumulated sugar phosphates, resulting in purine degradation, since the xylitol-induced increase in the NADH/NAD ratio partially blocked glycolysis at the level of GABP dehydrogenase. Therefore, administration of glucagon together with xylitol may synergistically increase purine degradation more than xylitol alone, despite decreases in the plasma concentration and urinary excretion of oxypurines.

Adult↗
PubMed1990

Purification, characterization and inhibition of D-3-aminoisobutyrate aminotransferase from the rat liver.

D-3-Aminoisobutyrate-pyruvate aminotransferase was purified 2000-fold from rat liver extract using heat treatment, ammonium sulfate fractionation, carboxylmethyl-Sepharose CL-6B, DEAE-Sepharose CL-6B, hydroxyapatite, Sephacryl S-200 and electrofocusing chromatographies. The purified enzyme was shown to be homogeneous by gel electrophoresis both in the presence and absence of SDS. Its molecular mass, determined by gel filtration, was 220 kDa and the subunit molecular mass was 52 kDa. The enzyme exhibited absorption maxima at 280 nm and 412 nm with a shoulder at 330 nm at neutral pH. The pH optimum for enzyme activity was 9.5 and the Km values for beta-alanine and pyruvic acid were calculated to be 0.81 mM and 0.45 mM, respectively. The purified enzyme catalyzed the transamination of omega-amino acids; beta-alanine and D-3-aminoisobutyric acid served as good amino donors, and pyruvic acid, glyoxylic acid and oxaloacetic acid were favorable amino acceptors. 6-Azauracil and 6-azathymine were found to be potent inhibitors of purified rat liver D-3-aminoisobutyrate-pyruvate aminotransferase. 6-Azauracil acted as a competitive inhibitor with respect to beta-alanine, and was an uncompetitive inhibitor with respect to pyruvic acid with a Ki of approximately 8.9 mM.

Animals↗
PubMed1978

Thiamin deficiency effects on rat leukocyte pyruvate decarboxylation rates.

Thiamin status usually is assessed by urinary excretion of thiamin or by exogenous thiamin pyrophosphate (TPP) stimulation of erythrocyte transketolase activity. Because of the possible great utility of a biologically and chemically sensitive alternative method for thiamin status assessment, studies were made of rat leukocyte pyruvate decarboxylation activity in thiamin deficiency. Pyruvate decarboxylation rates were determined by assaying 14CO2 produced by leukocytes from 1-14C-pyruvic acid in vitro. Reaction conditions were 5 mumoles pyruvic acid, 2.2 X 10(4) DPM 1-14C-pyruvic acid, leukocytes from 5 ml whole blood, 50 mumoles NaH2PO4, 5 mumoles MgSO4, and 1 mumole MnSO4 at pH 7.4 in 1 ml reaction volume at 25 C. Four weeks of thiamin deficiency decreased leukocyte pyruvate decarboxylation rates and markedly increased the TPP effect on this reaction. Dual weekly assays in the same rats showed that 21 days of thiamin deficiency significantly increased the TPP effect on leukocyte pyruvate decarboxylation rates. In contrast, the TPP effect on erythrocyte transketolase activity was significantly increased after only 7 days of thiamin deficiency. Erythrocyte transketolase is more sensitive than leukocyte pyruvate decarboxylation rate to early thiamin deficiency in rats.

Animals↗
PubMedDate not supplied

[Effect of a malic acid load on the blood and urine content in animals of the products of a malate dehydrogenase reaction and the correlation of reduced and oxidized forms of ascorbic acid].

Addition of 150 mg of malic acid per a day to food of rabbits caused an increase in content of reduced ascorbic acid and pyruvic acid in blood; at the same time the content of oxydized forms of ascorbic acid was decreased. Similar alterations were observed in urine of guinea-pigs, which received 100 mg of malic acid per a day. The data obtained suggest that under these conditions the increased reduction, of ascorbic acid was due to increased formation of NADP with H2 in the course of reaction, catalyzed by malate dehydrogenase.

Administration, Oral↗
PubMed2001

Evolution and stability of anthocyanin-derived pigments during Port wine aging.

For three years, the evolution of the three major anthocyanidin monoglucosides (malvidin 3-glucoside, malvidin 3-acetylglucoside, and malvidin 3-coumaroylglucoside) and their anthocyanin-pyruvic acid adducts was monitored in Port wines stored in oak barrels. The degradation reactions of all pigments followed first-order kinetics in all the wines studied. The degradation rate constants of the anthocyanin-pyruvic acid adducts were much lower than those of the anthocyanidin monoglucosides. The results of both anthocyanins and pyruvic acid adducts show that acylation on the sugar moiety of all the pigments decreased their stability in wine. The levels of malvidin 3-glucoside-pyruvic acid adduct and its acylated forms increased right after wine fortification with wine spirit before starting to decrease around 100 days. The initial formation of anthocyanin-pyruvic acid adducts was concurrent with the degradation of anthocyanidin monoglucosides.

Anthocyanins↗
PubMed1986

Survival under space vacuum--biochemical aspects.

Exposure to vacuum predominantly causes the removal of water. As a consequence hydrophobic bonds (e.g. of membranes and proteins) are disrupted and metabolism practically comes to a complete halt. Removal of hydrate water also causes substantial changes regarding the structure of DNA (A-structure likely prevails). Some organisms, however, especially bacterial spores and fungal conidia are so well adapted to extreme dryness that substantial fractions of these organisms survive several months of vacuum even at room temperature. In these organisms some vacuum-induced alterations occur that are not readily reversed by readdition of water; mutations become evident and the amount of DNA covalently bound to protein is drastically increased. The mechanisms of these processes and their possible repair are not yet clear. There is evidence that chemical reactions (e.g. dehydration reactions) are involved although they likely proceed at an extremely low rate. Using the dehydration of serin by vacuum as a model system (the resulting amino acrylic acid is converted into pyruvic acid and ammonia after reexposure to water) we could establish that about 3 out of 100 000 serins are finally converted into pyruvic acid after exposure to 10(-6) Torr for 1 week at 55 degrees C In dry Ar the corresponding rate is only about 1.5.

Adaptation, Physiological↗
PubMed1975

Pyruvate inhibition of the carbon dioxide fixation of the strict chemolithotroph Thiobacillus thiooxidans.

A flow-through dialysis system used to decrease the concentrations of toxic organic materials excreted by Thiobacillus thiooxidans permitted an improved efficiency of carbon dioxide fixation when compared with cells taken from the usual shaken culture. The additions of various concentrations of pyruvic acid and succinic acid inhibited growth significantly. Pyruvate at a concentration of 5 X 10(-3) M completely inhibited the respiration of resting cells oxidizing sulfur. The toxicity of pyruvic acid was found to be permanent as evidenced by the inability to obtain satisfactory oxidation rates after washing the exposed cells twice in buffer. Both pyruvate (10(-3) M) and succinate (10(-3) M) inhibited carbon dioxide fixation by 84%.

Acidithiobacillus thiooxidans↗
PubMed1976

Influence of growth temperature on glucose metabolism of a psychotrophic strain of Bacillus cereus.

The influence of temperature on glucose metabolism of a psychotrophic strain of Bacillus cereus was investigated. The pH of the growth medium and spore-forming frequencies of B. cereus varied when grown at 32, 20, or 7 C. Radiorespirometric analyses revealed that vegetative cells of B. cereus metabolized glucose by simultaneous operation of the Embden-Meyerhof-Parnas pathway and the pentose phosphate pathway. As the growth temperature decreased, glucose was metabolized with increased participation of the pentose phosphate pathway. The shift of cells grown at a higher temperature to a lower temperature increased the relative participation of the pentose phosphate pathway, whereas the shift of cells grown at low temperatures to a higher temperature had the opposite effect. Cells of late logarithmic phase grown at 20 and 7 C oxidized acetate by the tricarboxylic acid cycle reaction. However, cells grown at 32 C failed to oxidize acetate to CO2 to any appreciable extent. The extracellular products resulting from the metabolism of glucose decreased as the growth temperature was lowered. Organic acids were the major extracellular products of cultures grown at 32 and 20 C. Acetic acid, lactic acid, and pyruvic acid together accounted for 86.1 and 78.9% of extracellular radioactivity, respectively, at the two temperatures. The relative ratio of these three acids varied between the temperatures. Little or no acid accumulated at 7 C.

Acetates↗
PubMed1975

Changes in enzyme and metabolite content of effluent perfusate during preservation of dog kidneys by Collins' method.

Enzyme and metabolite content of effuent perfusate has been investigated. One kidney was removed from dogs and preserved by Collin's method. The animals were then bled to a mean arterial blood pressure of 5.26 KPa (40 mm Hg) and maintained at this pressure for 60 min after which the other kidney was removed and preserved in a similar way. 10-ml samples of effluent perfusate were taken immediately, and after 30 min, 1, 2, 3, 4, 6, 8, 24, 48 and 72 h. Acid phosphatase, arylsulphatase "A", ss-glucuronidase, LDH, leucin-aminopeptidase, lactic acid and pyruvic acid were determined by fluorometric methods. It was found that the activity of the enzymes rose parallel with the duration of preservation, the rise was especially great at 48 and 72 h. Activity of LDH and arylsulphatase "A" was significantly higher even at the beginning of preservation in the group of kidneys exposed in vivo to hypotension. This significant difference was present at 24, 48 und 72 h in the activity of all enzymes.

Acid Phosphatase↗
PubMed1992

[Studies on metabolism of a fungicide yekuling in rat].

The metabolism of a fungicide Yekuling was studied in rat after oral administration. Four metabolites were isolated and purified by means of reverse-phase HPLC and TLC. They were identified to be acetic acid, 1,3-dithiolan-2-ylidenehydrazide; pyruvic acid, 1,3-dithiolan-2-ylidenehydrazide; benzoic acid and hippuric acid with UV and MS. The latter was further confirmed by chemical synthesis. The experimental results showed that Yekuling was metabolized extensively in rat. Yekuling was hydrolyzed by amidase to produce benzoic acid and 1,3-dithiolan-2-ylidenehydrazide. The latter was further acetylated by N-acetyltransferase to form acetic acid, 1,3-dithiolan-2-ylidenehydrazide, or condensed spontaneously to form pyruvic acid, 1,3-dithiolan-2-ylidenehydrazide. Benzoic acid was further conjugated with glycine to produce hippuric acid.

Acetates↗
PubMed1976

Metabolic acidosis in status asthmaticus.

Blood gases and acid-base balance were measured in a group of patients in status asthmaticus. Simple or combined metabolic acidosis was found in 37.9% of the patients. In 25 of these, lactic acid (LA), pyruvic acid (PA) and LA/PA were increased. Increased glycolysis and anaerobic respiratory muscle glycolysis during extreme airways obstruction may be instrumental in these changes. Base deficit, not accounted for by organic acid increase, may be dependent on previously present hypocapnic hyperventilation. Possibly hyperlactemia provoked by hyperventilation may be exaggerated in severe asthma.

Acid-Base Equilibrium↗
PubMed1977

Effect of physical exercise on gastric basal secretion in healthy men.

Behaviour of basal gastric secretion of electrolytes, lactic acid and pyruvic acid was studied in twenty-minute portions in 14 healthy men in rest, during exercise and restitution. On bicycle ergometer in sitting position all studied men performed the average work 15 120 +/- 1800 kpm during 20 minutes. It was found that basic gastric secretion didn't change significantly during exercise, but its significant decrease occurred during twenty-minute restitution after exercise. During restitution secretion of Cl, Mg and Ca also significantly decreased while their concentrations didn't change in gastric juice. During physical exercise it was found the increase of lactic acid secretion in gastric juice; it was statistically significantly higher during restitution than in rest period (p less than 0.001) and during exercise (p less than 0.02).

Adult↗
PubMed1989

Usefulness of anaerobic threshold in estimating intensity of exercise for diabetics.

We examined the utility of the anaerobic threshold (AT) for quantifying the intensity of exercise that a diabetic patient is capable of handling. Thirteen diabetic patients treated with buformin exercised on a bicycle ergometer, and comparison was made with 20 healthy subjects matched for age and sex. The AT was determined from VO2 and VE with a personal computer. The intensity of exercise at the AT was 93 +/- 6 W in diabetic men and 80 +/- 10 W in diabetic women, values that were less than those of healthy subjects (P less than 0.05). There was a negative correlation between the intensity of exercise at the AT and the plasma concentration of buformin (P less than 0.01). There were no significant differences in either plasma lactic acid or pyruvic acid concentration at the AT between healthy subjects and diabetics. The plasma glucose at the AT or after exercise was lower than the baseline values in all subjects (P less than 0.01). The plasma insulin at the AT was lower than the baseline values in healthy subjects (P less than 0.01), but not in diabetics. There were no changes in plasma glucagon in any group. We concluded that determination of the AT is a simple, non-invasive procedure useful for ascertaining the optimal intensity of exercise for diabetics.

Adult↗
PubMed1983

Biosynthesis of amino acids from sucrose and Krebs cycle metabolites by Rhizobium lupini bacteroids.

The possibility of amino acids biosynthesis from sucrose, metabolites of Krebs cycle or glyoxylate and ammonium by intact bacteroids has been studied. The suspension of intact Rhizobium lupini bacteroids in phosphate buffer solution pH 7.8 was shown to catalyse the biosynthesis from sucrose and ammonium of some amino acids, such as alanine, aspartic and glutamic acids, glycine and serine. The yield of alanine and aspartic acid was 2.5-3 times higher than that of other amino acids, which were formed in almost equal quantities. Intact bacteroids were also found to catalyse the biosynthesis of aspartic and glutamic acids, alanine and glycine from ammonium and Krebs cycle metabolites such as fumaric acid (FA), oxaloacetic acid (OAA), pyruvic acid (PA), alpha-ketoglutaric acid (alpha-KGA), malic acid (MA), as well as from glyoxylic acid (GOA). The biosynthesis of aspartic acid from fumaric acid was dominant. Besides that, the suspension of intact bacteroids catalysed transamination of aspartic and glutamic acids, the transamination of aspartic acid being especially intense with alpha-KGA and GOA. Aspartic acid was synthesized most efficiently through the amination of fumaric acid, while glutamic acid was better synthesized through the transamination of aspartic acid with alpha-KGA than through reductive amination of alpha-KGA. The experimental data proved that intact bacteroids possess Krebs cycle enzymes and primary ammonia assimilation enzymes. This enzyme complex permits bacteroids to detoxify ammonia, which they produce using sucrose and metabolites of Krebs cycle as the sources of carbon. The data obtained are of great interest as they prove the importance of bacteroids in the synthesis of amino acids from ammonium which is formed in the course of N2-fixation, and sucrose available from leaves.

Amino Acids↗
PubMed2003

Malo-ethanolic fermentation in Saccharomyces and Schizosaccharomyces.

Yeast species are divided into the K(+) or K(-) groups, based on their ability or inability to metabolise tricarboxylic acid (TCA) cycle intermediates as sole carbon or energy source. The K(-) group of yeasts includes strains of Saccharomyces, Schizosaccharomyces pombe and Zygosaccharomyces bailii, which is capable of utilising TCA cycle intermediates only in the presence of glucose or other assimilable carbon sources. Although grouped together, these yeasts have significant differences in their abilities to degrade malic acid. Typically, strains of Saccharomyces are regarded as inefficient metabolisers of extracellular malic acid, whereas strains of Sch. pombe and Z. bailii can effectively degrade high concentrations of malic acid. The ability of a yeast strain to degrade extracellular malic acid is dependent on both the efficient transport of the dicarboxylic acid and the efficacy of the intracellular malic enzyme. The malic enzyme converts malic acid into pyruvic acid, which is further metabolised to ethanol and carbon dioxide under fermentative conditions via the so-called malo-ethanolic (ME) pathway. This review focuses on the enzymes involved in the ME pathway in Sch. pombe and Saccharomyces species, with specific emphasis on the malate transporter and the intracellular malic enzyme.

Animals↗
PubMed1983

High-performance liquid chromatography of alpha-keto acids in human saliva.

alpha-Keto acids in human mixed saliva collected without stimulation were analysed by reversed-phase ion-pair high-performance liquid chromatography (HPLC). Several alpha-keto acids were found in saliva and their concentrations were: alpha-ketoglutaric acid (KGA), 221 +/- 142; pyruvic acid (PA), 7490 +/- 5600; alpha-ketoisovaleric acid (KIVA), 61 +/- 23; alpha-ketoisocaproic acid (KICA), 137 +/- 79; alpha-keto-beta-methylvaleric acid (KMVA), 41 +/- 19 nmol/dl (mean +/- SD, n = 40). Their levels proved to be lower than those in plasma, except that of PA. Their concentrations in saliva showed individual variation compared with those in blood.

Adult↗
PubMed1991

Antioxidative properties of harmane and beta-carboline alkaloids.

beta-Carboline alkaloids are derived as a result of condensation between indoleamine (e.g. tryptamine) and short-chain carboxylic acid (e.g. pyruvic acid) or aldehyde (e.g. acetaldehyde), a reaction that occurs readily at room temperature. These compounds have been found endogenously in human and animal tissues and may be formed as a byproduct of secondary metabolism: their endogenous functions however, are not well understood. Indoles and tryptophan derivatives exhibit antioxidative actions by scavenging free radicals and forming resonance stabilized indolyl radicals. Harmane and related compounds exhibited concentration-dependent inhibition of lipid peroxidation (measured as thiobarbiturate reactive products) in a hepatic microsomal preparation incubated with either enzymatic dependent (Fe3+ ADP/NADPH) or non-enzymatic dependent (Fe3+ ADP/dihydroxyfumarate) oxygen radical producing systems. Alkaloids with hydroxyl substitution and a partially desaturated pyridyl ring were found to have the highest antioxidative potencies. Substitution of a hydroxyl group by a methoxyl group at the 6-position resulted in a decrease of greater than 10-fold in the antioxidative activities. Harmane showed high efficacy in an enzymatic system but low efficacy in a non-enzymatic system. The antioxidative effects of harmane in the former system may be attributed to its ability to inhibit oxidative enzymes in the microsomal system. These results suggest that beta-carbolines may also serve as endogenous antioxidants.

Animals↗