Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.1.1.27 (lactate dehydrogenase)
29,211 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Lactate oxidation catalysed by pig heart lactate dehydrogenase was studied in the presence of inhibitory concentrations of pyruvate. Experimental results show the presence of an intermediate which occurs immediately after the hydride transfer step, but before the dissociation of pyruvate and the H+ produced by the reaction. The rate constant for pyruvate dissociation and the dissociation constant for pyruvate from the ternary complex differ from those obtained in pyruvate reduction experiments. 2. In single-turnover pyruvate reduction by pig heart lactate dehydrogenase at pH8.0 pyruvate can bind to the enzyme before a H+ is taken up, and the subsequent uptake of a H+ is governed by a step that is also rate-limiting for single-turnover and steady-state NADH oxidation. 3. Observation of various intermediates in the single-turnover pyruvate reduction experiments has made it possible to determine separately the dissociation constant and Km value for pyruvate at pH8.0, and also the catalytic turnover rate and Km for pyruvate under first-order conditions at different pH values. 4. Further studies on single-turnover pyruvate reduction carried out in 2H2O, or in water at low temperature, show another step which, under these conditions, is slower than that controlling H+ uptake and rate-limiting for NADH oxidation. A scheme is presented which explains these results.
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PMID:Pig heart lactate dehydrogenase. Binding of pyruvate and the interconversion of pyruvate-containing ternary complexes. 0 75

The chain oxidation of lactate dehydrogenase-bound NADH initiated by superoxide radicals and propagated by oxygen was studied with pulse radiolysis. The kinetic parameters were re-evaluated in a system with carefully purified reagents (water and other chemicals) and in the presence of EDTA. The rate constant for the oxidation of the enzyme-bound NADH by O2- is calculated from the observed pseudo-first order disappearance of NADH and the chain length (molecules of NADH oxidized per O2- anion generated in the pulse). It is (1.0 +/- 0.2) X 10(5) M-1 S-1, consistent within a 13-fold variation in lactate dehydrogenase. NADH complex concentration and with varying chain length up to 6.1. Based on experiments with varying pH values from 4.5 to 9.0, the rate constant for oxidation of enzyme-bound NADH by HO2 is estimated to be 2.0 X 10(6) M-1 S-1.
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PMID:Re-evaluation of the kinetics of lactate dehydrogenase-catalyzed chain oxidation of nicotinamide adenine dinucleotide by superoxide radicals in the presence of ethylenediaminetetraacetate. 0 64

The stage of structures of the spinal reflex arc was studied by methods of quantitative cytochemistry in rats after orbital space flights lasting 19.5 and 22.5 days; the RNA and cytoplasmic protein content was determined in spinal motoneurons and sensory neurons of the spinal ganglia, the composition of soluble proteins of the gray and white matter of the spinal cord and spinal ganglia was determined; the lactate dehydrogenase (LD) isozyme spectrum also was investigated in the spinal ganglia and muscles of the hind limbs. A decrease in the content of cytoplasmic proteins in the spinal motoneurons and neurons of the spinal ganglia and a decrease in the content of water-soluble proteins in the gray and white matter of the spinal cord were found 5-11 h after space flight lasting 19.5 days and during the first day after a space flight lasting 22.5 days. Significant changes in the activity of isozyme fractions LD1 and LD2 were found in homogenates of the spinal ganglia. On the 1st and 2nd days after flight the LD isozyme spectrum of the soleus muscle changed from "cardiac" to "intermediate" type. The changes discovered were evidently the result of functional underactivity of the skeletal muscles under conditions of weightlessness. An increase in the RNA content in the sensory and motor neurons and an increase in the content of water-soluble proteins in the gray matter of the spinal cord were found 25-27 days after the end of the space flights, probably a manifestation of readaptation of the animals to terrestrial conditions.
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PMID:Development of metabolic shifts in structures of the spinal reflex arc in rats after space flight. 9 99

The plaque-derived gram-negative microorganism Y4 identified as a member of the genus Actinobacillus, was tested for a soluble cytotoxic factor(s). Sonication or incubation of viable Y4 microorganisms in distilled water or normal human serum resulted in liberation of a soluble material which was cytotoxic in vitro for human polymorphonuclear leukocytes (PMNs). The Y4 soluble sonic extract was also cytotoxic to human peripheral blood monocytes. However, human lymphocytes, platelets, and fibroblasts, as well as rabbit, rat, and mouse leukocytes and chicken embryo fibroblasts, were not killed by exposure to the Y4 sonic extract. No hemolytic activity was detected in the Y4 sonic extract. No hemolytic activity was detected in the Y4 sonic extract. Consequently, the factor(s) in the Y4 sonic extract was referred to as Y4 leukotoxin. The Y4 leukotoxin was inactive at 4 degrees C, heat sensitive (56 degrees C, 30 min), and inactivated by proteases. The cytotoxic effect of Y4 leukotoxin on PMNs was dose, time, and temperature dependent. The leukotoxin did not bind to viable PMNs at 4 degrees C but did bind to dead PMN membrane components at both 4 and 37 degrees C. The addition of bovine serum albumin (51 mg/ml) to PMN-Y4 leukotoxin cultures inhibited the release of lactate dehydrogenase from the PMNs, but did not prevent the death of the cells as indicated by electron microscopy. Lysosomal markers were released in parallel to the cytoplasmic enzyme lactate dehydrogenase from Y4 leukotoxin-treated PMNs. The addition of 0.02 M ethylenedinitrilotetraacetic acid to these cultures inhibited release of lysosomal markers but enhanced the release of lactate dehydrogenase. These results suggested that a soluble leukotoxin with specificity for only human PMNs and monocytes can be liberated from viable Y4. What role this leukotoxin plays in the pathogenicity of the Y4 microorganism is not yet known. However, this leukotoxin is one of the first materials from a plaque-derived microorganism with a potential role in the pathogenesis of juvenile periodontitis.
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PMID:Extraction and partial characterization of a leukotoxin from a plaque-derived Gram-negative microorganism. 11 47

The rate constants and equilibrium constants of the individual steps of several enzyme reactions may be determined by the application of rapid reaction methods and isotope techniques. This makes it possible to complement the formalism of the Haldane relation with details of the reaction mechanism. It has been shown that, in several enzyme reactions, steps involving chemical catalysis are fast and have small free-energy changes compared with those of the substrate binding and product dissociation processes. Data are presented in this paper for three enzyme reactions for which different methods have been used to elucidate the kinetic parameters of the elementary steps. For cardiac lactate dehydrogenase (EC 1.1.1.27), absorption and fluorescence spectroscopy have been used to distinguish the step involved in the chemical process from those involved in the formation of the substrate complex and the release of the product. The rate of interconversion between enzyme-bound substrates and products is fast compared with other steps and the equilibrium constant for the process is near unity. Consequently, the difference of standard free energy changes for the formation of the two ternary complexes correspons approximately to the overall free-energy change of the hydrogen transfer reaction. Isotope kinetic techniques can be used to study the reactions of triosephosphate isomerase (EC 5.3.1.1). With this enzyme, the interconversion of enzyme-bound substrate into product is comparable in rate to product dissociation. The reactions of myosin subfragment 1 with ATP, studied by fluorescence spectroscopy and chemical quenching, follow a similar pattern in that the equilibrium constant of the chemical step in which water reacts with protein-bound ATP is 9. In this case, however, there is a remarkably large free-energy change associated with a first-order process involved in the binding of ATP. The possible significance of these results to energy transduction in muscle contraction as well as in the biosynthesis of ATP is discussed.
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PMID:Energy changes during the formation and interconversion of enzyme-substrate complexes. 12 90

The effect of prolonged digoxin treatment (1 mg/kg day for 8 days) on the activity levels of some enzymes of energy metabolism (phosphofructokinase, lactate dehydrogenase, citrate synthase, succinate dehydrogenase) in rat myocardium was studied. In the control animals receiving the solvent mixture (glycerol:ethanol:water in 1:1:1) a transient decrease in the lactate dehydrogenase and citrate synthase activity levels was observed. In the hearts of digoxin treated rats the level of activity of phosphofructokinase was permanently lowered by the fourth day and the level of activity of citrate synthase permanently increased after the first day of treatment. A transient increase in the activity level of succinate dehydrogenase in the myocardium of digoxin treated animals was seen between days 1 and 6. In this study a permanent decrease in phosphofructokinase and an increase in citrate synthase activity levels in rat heart muscle was noted during prolonged digoxin treatment.
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PMID:Enzyme activities of myocardial energy metabolism during prolonged digoxin treatment in rats. 14 96

Alkylation at N-1 of the NAD+ adenine ring with 3,4-epoxybutanoic acid, followed by chemical reduction to the alkali-stable NADH form and alkaline Dimroth rearrangement, gave the NADH derivative alkylated at the exocyclic adenine amino group. Enzymic reoxidation of the latter derivative gave nicotinamide-6-(2-hydroxy-3-carboxypropylamino)purine dinucleotide, a functionalized NAD+ analogue carrying an omega-carboxyalkyl side-chain at the exocyclic adenine amino group. Carbodiimide coupling of the latter derivative to high-molecular-weight water-soluble (polyethyleneimine, polylysine) and insoluble (aminohexyl-Sepharose) polymers gave the corresponding macromolecularized NAD+ analogues. These derivatives have been shown to be enzymically reducible. The polyethyleneimine and polylysine analogues showed a substantial degree of efficiency relative to free NAD+ with rabbit muscle lactate dehydrogenase (60 and 25% respectively) but a lower one with yeast alcohol dehydrogenase and Bacillus subtilis alanine dehydrogenase (2-7%). The polyethyleneimine derivative entrapped in cellulose triacetate fibres together with the lactate dehydrogenase was operationally stable during repetitive use.
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PMID:Synthesis of coenzymically active soluble and insoluble macromolecularized NAD+ derivatives. 17 91

Phosphoglycerate mutase is phosphorylated on a histidine residue by the cofactor of the reaction, 2,3-bisphosphoglycerate (Rose, Z. B. (1970) Arch. Biochem. Biophys. 140, 508-513). The phosphoryl group is readily transferred to the normal acceptors, 3-phosphoglycerate and 2-phosphoglycerate, or to water in the presence of glycolate-2-P. An acid-labile phosphorylated decapeptide has been purified from a tryptic digest of the phosphoenzyme. The amino acid sequence of the peptide has been determined to be: Aal-Gly-Gln-Leu-Asp-Glu-Ser-His-Arg. This sequence bears a striking analogy to part of a highly conserved region of lactate dehydrogenase (residues 100 to 109) (Taylor, S. S., Oxley, S. S., Allison, W. S., and Kaplan, N. O. (1973) Proc. Natl. Acad. Sci. U. S. A. 70, 1970-1974). Evidence from x-ray crystallographic studies indicates that the two enzymes are similar in tertiary structure (Campbell, J. W., Watson, H. C. and Hodgson, G. I. (1974) Nature 250, 301-303).
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PMID:The sequence of a peptide containing the active site phosphohistidine residue of phosphoglycerate mutase from chicken breast muscle. 17 Feb 78

Reaction in dimethyl sulfoxide of nicotinamide 8-bromoadenine dinucleotide with the disodium salt of 3-mercaptopropionic acid afforded nicotinamide-8-(2-carboxyethylthio)adenine dinucleotide, a new NAD+ analogue functionalized at the adenine C-8 position by an omega-carboxylic side chain. Carbodimide coupling of the latter derivative to high-molecular-weight water-soluble (polyethyleneimine, polylysine) and insoluble (aminohexy)-Sepharose) polymers gave the corresponding macromolecular NAD+ analogues. These derivatives have been shown to be enzymically reducible. The polyethyleneimine analogue showed a substantial degree of efficiency relative to free NAD+ with yeast alcohol dehydrogenase (47%) but a considerably lower one with rabbit muscle lactate dehydrogenase (3%); the polylysine analogue showed a low degree of efficiency with both enzymes (5-6%).
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PMID:New coenzymically-active soluble and insoluble macromolecular NAD+ derivatives. 17 13

1. A method is described for the isolation of rat parotid acinar cells by controlled digestion of the gland with trypsin followed by collagenase. As judged by Trypan Blue exclusion, electron microscopy, water, electrolyte and ATP concentrations and release of amylase and lactate dehydrogenase, the cells are morphologically and functionally intact. 2. A method was developed for perifusion of acinar cells by embedding them in Sephadex G-10. Release of amylase was stimulated by adrenaline (0.1-10muM), isoproternol (1 or 10 MUM), phenylephrine (1 muM), carbamoylcholine (0.1 or 1 muM), dibutyryl cycle AMP (2 MM), 3-isobutyl-1-methylxanthine (1mM) and ionophore A23187. The effects of phenylephrine, carbamoylcholine and ionophore A23187 required extracellular Ca2+, whereas the effects of adrenaline and isoproterenol did not. 3. The incorporation of 45Ca into parotid cells showed a rapidly equilibrating pool (1-2 min) corresponding to 15% of total Ca2+ and a slowly equilibrating pool (greater than 3h) of probably a similar dimension. Cholinergic and alpha-adrenergic effectors and ionophore A23187 and 2,4-dinitrophenol increased the rate of incorporation of 45Ca into a slowly equilibrating pool, whereas beta-adrenergic effectors and dibutyryl cyclic AMP were inactive. 4. The efflux of 45Ca from cells into Ca2+-free medium was inhibited by phenylephrine and carbamoylcholine and accelerated by isoproterenol, adrenaline (beta-adrenergic effect), dibutyryl cyclic AMP and ionophore A23187. 5. A method was developed for the measurement of exchangeable 45Ca in mitochondria in parotid pieces. Incorporation of 45Ca into mitochondria was decreased by isoproterenol, dibutyryl cyclic AMP or 2,4-dinitrophenol, increased by adrenaline, and not changed significantly by phenylephrine or carbamoylcholine. Release of 45Ca from mitochondria in parotid pieced incubated in a Ca2+-free medium was increased by isoproterenol, adrenaline, dibutyryl cyclic AMP or 2,4-dinitrophenol and unaffected by phenylephrine or carbamoylcholine. 6. These findings are compatible with a role for Ca2+ as a mediator of amylase-secretory responses in rat parotid acinar cells, but no definite conclusions about its role can be drawn in the absence of knowledge of the molecular mechanisms involved, their location, and free Ca2+ concentration in appropriate cell compartment(s).
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PMID:Calcium metabolism and amylase release in rat parotid acinar cells. 18 53


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