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Query: EC:4.1.2.13 (aldolase)
 3,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxygen (18) was used as a mechanistic probe in the investigation of several different sources of fructose 1,6-bisphosphate aldolases (EC 4.1.2.13) which, due to differences in some physical and chemical properties, could not be clearly put in either Class I or Class II. Aldolases may be identified as belonging to a particular class on the basis of the amount of 180 retained in the dihydroxyacetone phosphate produced in the cleavage of [2-Oxygen (18)] fructose 1,6-biphosphate. The mechanism of Class I aldolases involves an obligatory exchange of the C-2 oxygen atom of fructose 1,6-bisphosphate, leading to the absence of 180 in the product. For Class II aldolases, the C-2 oxygen atom is retained in the aldol cleavage reaction. Aldolases from spinach and L. casei base intermediate. Aldosase from C. perfringens was found to be Class II, suggesting a metal-chelate intermediate. Results with Euglena aldolase confirmed that this organism contained both types of aldolases with approximately 78% Class II. The data show that despite a wide variety of physical and chemical properties, there are important mechanistic similarities within each class of enzyme and significant differences between the two classes. The determination of 180 retention in the product of the cleavage reaction using [2-180] fructose 1,6-biphosphate is an accurate means of classifying these enzymes since it is a measure of a property which is directly related to the mechanisms of the reactions.
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PMID:Classification of fructose-1,6-bisphosphate aldolases based on 18O retention in the cleavage reaction. 17 Sep 73

One of the obligate thermophilic bacteria, Bacillus stearothermophilus, was unable to grow at temperatures below 35 degrees C. About 80% of the population in the bacterial culture died at the temperatures, and the same extent of loss in either of the activities of oxygen consumption or synthesis of protein or nucleic acid of the organisms was observed. With the progress of death of the organisms, reduced nicotinamide-adenine dinucleotide came to be oxidized by the organisms, enzymes such as fructose-1,6-diphosphate aldolase, when the organisms were washed with phosphate buffer, were leaked out of the organisms, and an increasing amount of ribonucleoprotein was released into the culture medium. The change of the membrane state was then suggested to be one of the possible causes for the death of the organisms at the temperatures.
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PMID:Effect of temperature on the viability of Bacillus stearothermophilus. 17 53

In Escherichia coli, L-fucose is dissimilated via an inducible pathway mediated by L-fucose permease, L-fucose isomerase, L-fucose kinase, and L-fuculose 1-phosphate aldolase. The last enzyme cleaves the six-carbon substrate into dihydroxyacetone phosphate and L-lactaldehyde. Aerobically, lactaldehyde is oxidized to L-lactate by a nicotinamide adenine dinucleotide (NAD)-linked dehydrogenase. Anaerobically, lactaldehyde is reduced by an NADH-COUPLED REDUCTASE TO L-1,2-propanediol, which is lost into the medium irretrievably, even when oxygen is subsequently introduced. Propanediol excretion is thus the end result of a dismutation that permits further anaerobic metabolism of dihydroxy-acetone phosphate. A mutant selected for its ability to grow aerobically on propanediol as a carbon and energy source was reported to produce lactaldehyde reductase constitutively and at high levels, even aerobically. Under the new situation, this enzyme serves as a propanediol dehydrogenase. It was also reported that the mutant had lost the ability to grow on fucose. In the present study, it is shown that in wild-type cells the full synthesis of lactaldehyde dehydrogenase requires the presence of both molecular oxygen and a small molecule effector, and the full synthesis of lactaldehyde reductase requires anaerobiosis and the presence of a small molecule effector. The failure of mutant cells to grow on fucose reflects the impairment of a regulatory element in the fucose system that prevents the induction of the permease, the isomerase, and the kinase. The aldolase, on the other hand, is constitutively synthesized. Three independent fucose-utilizing revertants of the mutant all produce the permease, the isomerase, the kinase, as well as the aldolase, constitutively. These strains grow less well than the parental mutant on propanediol.
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PMID:Disruption of the fucose pathway as a consequence of genetic adaptation to propanediol as a carbon source in Escherichia coli. 18 64

1. The regulation of glycolysis and pyruvate oxidation under varying conditions of ATP and oxygen consumption was studied in isolated perfused rat hearts. Potassium-induced arrest was employed to inhibit the ATP consumption of the heart. 2. Under the experimental conditions, the beating heart used solely glucose as the oxidisable substrate. The glycolytic flux through the aldolase step decreased in pace with the decreasing oxygen consumption during the potassium-induced arrest of the heart. The decrease in glucose oxidation was larger than the inhibition of the oxygen consumption, suggesting that the arrested heart switches to fatty acid oxidation. The time course and percentage changes of the inhibition of pyruvate oxidation and the decrease in the amount of the active form of pyruvate dehydrogenase suggest that the amount of active pyruvate dehydrogenase is the main regulator of pyruvate oxidation in the perfused heart. 3. To test the relative significance of the possible mechanisms regulating covalent interconversions of pyruvate dehydrogenase, the following parameters were measured in response to the potassium-induced cardiac arrest: concentrations of pyruvate, acetyl-CoA, CoA-SH, citrate, alpha-oxoglutarate, ATP, ADP, AMP, creatine, creatine phosphate and inorganic phosphate and the mitochondrial NADH/NAD+ ratio. In cardiac tissue the adenylate system is not a good indicator of the energy state of the mitochondrion, even when the concentrations of AMP and free cytosolic ADP are calculated from the adenylate kinase and creatine kinase equilibria. Only creatine phosphate and inorganic phosphate undergo significant changes, but evidence of the participation of the latter compounds in the regulation of the pyruvate dehydrogenase interconversions is lacking. The potassium-induced arrest of the heart resulted in a decrease in pyruvate, a slight increase in acetyl-CoA, a large increase in the concentration of citrate and an increase in the mitochondrial NADH/NAD+. The results can be interpreted as showing that in the heart, the pyruvate dehydrogenase interconversions are mainly regulated by the pyruvate concentration and the mitochondrial redox state. Concentrations of all the regulators tested shifted to directions which one would expect to result in a decrease in the amount of active pyruvate dehydrogenase, but the changes were quite small. Therefore, the energy-linked regulation of pyruvate dehydrogenase in intact tissue is possibly mediated by the equilibrium relations between the cellular redox state and the phosphorylation potential recently confirmed in cardiac tissue.
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PMID:Energy-linked regulation of glucose and pyruvate oxidation in isolated perfused rat heart. Role of pyruvate dehydrogenase. 18 44

Injury induced in Escherichia coli cells by chlorination was studied from a physiological standpoint. Predictable and reproducible injury was found to occur rapidly in 0.5 mg of chlorine per liter and was reversible under nonselective conditions. There was an extended lag period in the growth of chlorinated cells not seen in control suspensions followed by the resumption of logarithmic growth at a rate equaling that of control cells. The aldolase activity of cells chlorinated in vivo was equivalent to that obtained for control cells. Oxygen uptake experiments showed that chlorinated cells underwent a decrease in respiration that was not immediatedly repaired in the presence of reducing agents. This effect was more pronouned in rich media containing reducing agents. Uptake of metabolities was inhibited by chlorine injury as shown with experiments using 14C-labeled glucose and algal protein hydrolysate.
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PMID:Chlorine injury and the enumeration of waterborne coliform bacteria. 37 30

Wild-type strains of Escherichia coli are unable to use L-1,2-propanediol as a carbon and energy source. Strain 3, a mutant selected for the ability to grow on this compound at progressively more rapid rates, synthesizes constitutively a nicotinamide adenine dinucleotide-linked propanediol oxidoreductase. This enzyme is normally synthesized during anaerobic growth on L-fucose when it functions as a lactaldehyde reductase. Propanediol, the end product of this fermentation process, escapes irretrievably into the medium. The propanediol-utilizing mutant can no longer grow on fucose in either the presence or absence of molecular oxygen. In the present study nine independent lines of propanediol-positive mutants were characterized. One mutant, strain 418, attained a propanediol growth rate close to that of strain 3 without loss of the ability to grow on fucose. In all cases examined, however, prolonged selection on propanediol did result in the emergence of fucose-negative mutants. All of these mutants had enzyme patterns similar to that of strain 3; namely, fucose permease, fucose isomerase, and fuculose kinase were noninducible, whereas fuculose 1-phosphate aldolase was constitutive. In strain 418 and in the fucose-positive predecessors of the other mutants, the first four enzymes in the pathway remained inducible, as in the wild-type strain. Improvements in the growth rate on propanediol appeared to reflect principally the increased activity level of the oxidoreductase during the early stages of evolution. According to transductional analysis, the mutations affecting the ability to grow on propanediol and those that affect the expression of the first enzymes in the fucose pathway were very closely linked. The loss of the ability to grow on fucose is thought to be a mechanistic consequence incidental to the remodeling of the regulatory system in favor of the utilization of the novel carbon source.
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PMID:Regulatory changes in the fucose system associated with the evolution of a catabolic pathway for propanediol in Escherichia coli. 40 Jul 96

The effect of perfluorochemical (PFC) emulsion (25 w/v per cent of PFC concentration) on carbon monoxide poisoning was studied in rats exposed to 97 per cent O2 and three per cent CO. There was no significant difference in conversion rate of hemoglobin to carboxyhemoglobin (COHb) between PFC emulsion and saline groups. However, after re-exposure to pure oxygen, PFC emulsion group circulation reconverted to oxyhemoglobin (OXYHb) at a significantly faster rate than circulation in the control group. Survival time of rats was considerably affected by infusion of PFC emulsion and prolonged in proportion to increased injection dosage. Significant elevations in plasma glucose, lactate and aldolase levels and lactate/pyruvate ratio were found in the saline group and these levels remained well within normal range in the PFC emulsion group. These results indicate that PFC emulsion can function as an oxygen carrier in the presence of carbon monoxide and can deliver sufficient oxygen to peripheral tissues.
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PMID:Effect of perfluorochemical (PFC) emulsion on acute carbon monoxide poisoning in rats. 73 57

Seven enzymes of the Embden-Myerhof pathway of glycolysis were assayed in hypotonically treated epididymal sperm from mature rabbits. These were: fructose-biphosphate aldolase, triosephosphate isomerase, glyceraldehydephosphate dehydrogenase, 3-phosphoglyceromutase, enolase, pyruvate kinase, and lactate dehydrogenase. These enzymes were firmly enough bound to the cell structure to resist removal by washing after hypotonic treatment and had maximal activities comparable to, or greater than, the rate of mitochondrial pyruvate oxidation, so that rapid oxygen uptake was observed with intermediates of the glycolytic pathway. The activity of lactate dehydrogenase in a typical preparation of hypotonically treated cells was 5.3 mumoles/minute x 10(9) cells at 25 degrees C for pyruvate reduction in the hypotonically treated cells and 4.8 mumoles/minute x 10(9) cells in the thrice-washed hypotonically treated cells. The Km for pyruvate was 1.4 mM while that for lactate was 4.4 mM. By contrast, the maximal activity of pyruvate oxidation by mitochondria was 0.10 microgram atom of oxygen/minute x 10(9) cells, corresponding to 0.020 mumole of pyruvate/minute x 10(9) cells, and the Km for pyruvate was 5 microM. These enzyme parameters favor high lactate production from glucose in aerobic glycolysis.
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PMID:Energy metabolism of spermatozoa. V. The Embden-Myerhof pathway of glycolysis: activities of pathway enzymes in hypotonically treated rabbit epididymal spermatozoa. 80 42

In 38 patients with chronic renal insufficiency of different degree of severity examinations of the stationary concentration of the adenine nucleotides in the erythrocytes were carried out. It was shown that in the red blood cells of uraemics a genuine increase of the concentration of these compounds occurs, in which case the adenosine triphosphate dominates absolutely as well as relatively. In individual cases erytho-cyctic ATP-values of more than 3 micron mol pro ml cells may be achieved. The increase of the ATP-concentration in the red blood cells correlates with the degree of severity of the renal insufficiency and the renal anaemia. The hyperphosphataemia occurring as a rule in renal insuficiency is of causal importance for the increase of ATP. By a consecutive increase of the intracellular phosphate level and by influence on different steps of enzymes (phosphofructokinase, aldolase, glycerin aldehyde phosphate dehydrogenase) and changed regulations it effected an activation of the glycolysis. The increase of the plasma adenine and plasma adenosine concentration plays apparantly an accessory role for the increase of the concentration of the adenine nucleotides existing in the erythrocytes. Together with an increased concentration of 2,3-diphosphogycerate (2,3-DPG) the increase of the ATP-level has an effect on the oxygen transport function function of haemoglobin in the sense of a facilitation of the O2-output. These processes explain the relative adaption of patients with chronic renal insufficiency to renal anaemias of partly high degree.
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PMID:[Adenine nucleotide- and 2,3-diphosphoglycerate metabolism in human erythrocytes in chronic kidney insufficiency]. 84 44

myo-Inositol-1-P synthase (EC 5.5.1.4) purified from rat testis and from bovine testis was allowed to react with D-[5-18O]glucose-6-P. myo-Inositol, obtained in these reactions, retained all of the 18O originally in the glucose-6-P. When these enzyme preparations were incubated with unlabeled glucose-6-P in a medium enriched in H2 18O no uptake of the oxygen isotope occurred that could be ascribed to the myo-inositol-1-P synthase reaction. By these criteria this enzyme, which is considered to use an aldolase mechanism in the cyclization step, cannot form a Schiff base during the reaction. In addition, these enzymes are not inhibited by 10 mM EDTA. One interpretation of this evidence is that the myo-inositol-1-P synthases we have studied are neither Class I nor Class II aldolases, and simply use base catalysis in the cyclization step.
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PMID:Incubations of testis myo-inositol-1-phosphate synthase with D-(5-18O)glucose 6-phosphate and with H218O show no evidence of Schiff base formation. 88 73


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