Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.5.3 (complex I)
 8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the subcommissural organ (SCO) of the guinea pig, rat, golden hamster, and mouse the activity and distribution of enzymes related to the energy-supplying metabolism and of some marker enzymes of different cell organelles have been investigated by means of mostly modified histochemical methods. The results were compared with findings in the ciliated ependyma of the ventricular wall and with those in the ependyma of the choroid plexus of the third ventricle. In the ependymal part of the SCO only a moderate activity of hexokinase is observed in its specialized columnar cells whereas a high activity is present both in the ciliated ependyma and the choroid plexus. - The staining pattern of glucose-6-phosphatase is similar to that of hexokinase but this enzyme is found is the SCO only. - Likewise hexokinase, glycogen granules and enzymes related to glycogen metabolism (phosphoglucomutase, uridine-diphosphoglucose pyrophosphorylase, glycogen synthetase and phosphorylase) are regularly found most numerous and active in the nuclear and supra-nuclear area of the ependymal part. These enzymes are less active in both the other ependymal regions. - Uridine-diphosphoglucose dehydrogenase could not be demonstrated in the SCO. The NADP-linked enzymes of the pentose phosphate shunt, glucose-6-phosphate and 6-phosphogluconate dehydrogenase, show a moderate activity which decreases also from the nuclear towards the apical area of the ependymal cells of the SCO. Enzymes of the glycolytic pathway, such as glucosephosphate isomerase, fructose-6-phosphate kinase, fructose-I,6-diphosphate aldolase, glyceraldehyde-3-phosphate and lactate dehydrogenase, are highly active in the SCO and are located mainly in the supranuclear area, too. Fructose-1,6-diphosphatase could not be demonstrated thus indicating that in the SCO the pathway is most probably only glycolytic but not gluconeogenetic. Compared to the ependyma of the ventricular wall and of the choroid plexus, in the SCO the M type subunits of lactate dehydrogenase predominate. Glycolytic enzymes are also very active in the choroid plexus but less in the ciliated ependyma. Compared to the ciliated ependyma and especially to the ependyma of the choroid plexus, the activities of enzymes which are only present in mitochondria (NAD-linked isocitrate dehydrogenase, succinate dehydrogenase, NAD-linked malate dehydrogenase after preextraction, cytochrome oxidase, 3-hydroxybutyrate and glycerolphosphate and glutamate dehydrogenase) are relatively low. Mitochondria are accumulated near the superior pole of the nuclei as well as in the most apical part of the ependymal cells. - The staining pattern of NADP-linked isocitrate and malate dehydrogenase as well as of NADH dehydrogenase suggests that these enzymes are localized both in and out of mitochondria. The extramitochondrial activity of the first two enzymes might be localized in the cytosol. The extramitochondrial activity of NADH dehydrogenase might be localized in the endoplasmic reticulum...
 ...
PMID:Enzymatic organization of the subcommissural organ. 123 49

Rapid malonate-sensitive transitory formation of enol-oxaloacetate followed by slow ketonization of the product was observed after addition of malate to the mammalian succinate-ubiquinone reductase in the presence of electron acceptor. The initial rate of enol-oxaloacetate production was equal to that of malate oxidation. Oxaloacetate keto-enol tautomerase had no effect on the initial rate of enol-oxaloacetate production nor on the kinetics of malate oxidation; the enzyme drastically accelerated the ketonization of the product. The solubilized and partially purified membrane-bound flavine adenine dinucleotide-dependent malate dehydrogenase from Acetobacter xylinum catalyzed oxidation of L- and D-malate without formation of enol-oxaloacetate as an intermediate of the reaction.
 ...
PMID:Direct demonstration of enol-oxaloacetate as an immediate product of malate oxidation by the mammalian succinate dehydrogenase. 186 83

The effects of arachidonic acid on the enzyme complexes in the electron transport system were investigated using submitochondrial particles from rat brain. Arachidonic acid irreversibly inhibited NADH-CoQ oxidoreductase (complex I) activity, but had no effect on the activities of succinate-CoQ oxidoreductase (complex II), CoQH2-cytochrome c oxidoreductase (complex III), cytochrome c oxidase (complex IV), ATPase (complex V), glutamate dehydrogenase, and malate dehydrogenase up to 50 microM. The inhibition was dose-dependent with an IC50 value of 110 nmol/mg protein. The Lineweaver-Burk plot revealed that the inhibition by arachidonic acid was noncompetitive against CoQ with a Ki value of 33 microM and uncompetitive against NADH with a Ki value of 22 microM.
 ...
PMID:Selective inhibition of NADH-CoQ oxidoreductase (complex I) of rat brain mitochondria by arachidonic acid. 190 30

The binding of porcine heart mitochondrial malate dehydrogenase and beta-hydroxyacyl-CoA dehydrogenase to bovine heart NADH:ubiquinone oxidoreductase (complex I), but not that of bovine heart alpha-ketoglutarate dehydrogenase complex, is virtually abolished by 0.1 mM NADH. The malate dehydrogenase and beta-hydroxyacyl-CoA enzymes compete in part for the same binding site(s) on complex I as do the malate dehydrogenase and alpha-ketoglutarate dehydrogenase complex enzymes. Associations between mitochondrial malate dehydrogenase and bovine serum albumin were observed. Subtle convection artifacts in short-time centrifugation tests of enzyme association with the Beckman Airfuge are described. Substrate channeling of NADH from both the mitochondrial and cytoplasmic malate dehydrogenase isozymes to complex I and reduction of ubiquinone-1 were shown to occur in vitro by transient enzyme-enzyme complex formation. Excess apoenzyme causes little inhibition of the substrate channeling reaction with both malate dehydrogenase isozymes in spite of tighter equilibrium binding than the holoenzyme to complex I. This substrate channeling could, in principle, provide a dynamic microcompartmentation of mitochondrial NADH.
 ...
PMID:Substrate channeling of NADH and binding of dehydrogenases to complex I. 250 78

Highly purified succinate-ubiquinone reductase catalyzes the oxidation of L- or D-malate with a Km and initial Vmax equal to approximately 10(-3) M and approximately 100 nmol/min/mg of protein, respectively. The malate dehydrogenase activity of succinate dehydrogenase rapidly decreases regardless of the presence of glutamate plus glutamate-oxaloacetate transaminase. The inhibitor trapping system, however, prevents the inactivation of succinate dehydrogenase under the conditions when the rate of tautomeric oxaloacetate enol in equilibrium oxaloacetate ketone interconversion is high. These results suggest that enol oxaloacetate is an immediate product of malate oxidation at the succinate dehydrogenase active site. Two proteins (Mr 37 and 80 kD) which catalyze the oxaloacetate tautomerase reaction were isolated from the mitochondrial matrix. Some physico-chemical and kinetic properties of these enzymes were characterized. The larger protein was identified as inactive aconitase. The system containing succinate dehydrogenase, L-malate, glutamate plus transaminase and oxaloacetate tautomerase was reconstituted. Such a system is capable of oxidizing malate to aspartate without rapid inactivation of succinate dehydrogenase. Taken together, the data obtained emphasize a significant role of enzymatic oxaloacetate tautomerization in the control of the succinate dehydrogenase activity in the mitochondrial matrix.
 ...
PMID:Regulation of succinate dehydrogenase and tautomerization of oxaloacetate. 262 74

The synthesis of isocitrate lyase was induced by the presence of ethanol in the chemostat reaching a specific activity of 200 mU X mg-1 at this induced state. In glucose-limited, derepressed cells, 20 mU X mg-1 were detected and under repressed conditions isocitrate lyase activity was not detected. The sensitivity of gluconeogenic enzymes: cytoplasmic malate dehydrogenase; fructose 1,6-bisphosphatase and isocitrate lyase as well as the mitochondrial enzymes NADH dehydrogenase and succinate cytochrome c oxidase to glucose and galactose repression were studied in chemostat cultures. Our results show that galactose was less effective as a repressor than glucose. Malate dehydrogenase was completely inactivated by glucose, whereas galactose only produced a 78% decrease of specific activity. Fructose 1,6-bisphosphatase and isocitrate lyase were completely inactivated by both sugars but at different rate. Glucose produced an 85% decrease of specific activity of the mitochondrial enzymes whereas galactose only decrease an 67%.
 ...
PMID:Differential sensitivities to glucose and galactose repression of gluconeogenic and respiratory enzymes from Saccharomyces cerevisiae. 300 23

Growth of Mycobacterium phlei under low oxygen tension resulted in specific activities two to twenty times lower for formate dehydrogenase, malate dehydrogenase, beta-hydroxybutyrate dehydrogenase, lactate oxidase and NADH dehydrogenase than when cultures were grown under high aeration. An increase in fumarate reductase and succinate dehydrogenase occurred with M. phlei grown under low oxygen tension. Malate: vitamin K dehydrogenase and glucose-6-phosphate dehydrogenase activity were not significantly affected by the oxygen tension used to grow the bacteria, and neither culture contained a lactate dehydrogenase. With growth of M. phlei in conditions of low oxygen tension, cytochrome a was not detected, but cytochrome b was prominent in membranes and cytochrome c was present in the soluble fraction.
 ...
PMID:Influence of oxygen tension on the respiratory activity of Mycobacterium phlei. 318 14

Succinate:ubiquinone reductase was shown to catalyze the oxidation of L- and D-stereoisomers of malate by artificial electron acceptors and ubiquinone. The rate of malate oxidation by succinate:ubiquinone reductase is by two orders of magnitude lower than that for the natural substrate--succinate. The values of kinetic constants for the oxidation of D- and L-stereoisomers of malate are equal to: V infinity = 0.1 mumol/min/mg protein, Km = 2 mM and V infinity = 0.05 mumol/min/mg protein, Km = 2 mM, respectively. The malate dehydrogenase activity is fully inhibited by the inhibitors of the dicarboxylate-binding site of the enzyme, i.e., N-ethylmaleimide and malonate and is practically insensitive to carboxin, a specific inhibitor of the ubiquinone-binding center. The enol form of oxaloacetate was shown to be the product of malate oxidation by succinate:ubiquinone reductase. The kinetics of inhibition of the enzyme activity by the ketone and enol forms of oxaloacetate was studied. Both forms of oxaloacetate effectively inhibit the succinate:ubiquinone reductase reaction.
 ...
PMID:[Malate oxidation by mitochondrial succinate:ubiquinone-reductase]. 339 46

A rapid decrease in male fertility in laboratory animals exposed to 1,2-dibromo-3-chloropropane (DBCP) has been suggested to be due, in part, to a postglycolytic inhibition of sperm carbohydrate metabolism. The present studies were performed to identify the specific site of DBCP-induced inhibition of intermediary metabolism. 14CO2 generation by epididymal sperm, isolated from Fischer 344 rats, was measured using radiolabeled tricarboxylic acid (TCA) cycle intermediates: acetyl CoA, citrate, alpha-ketoglutarate, and succinate. There was 0-28% inhibition of CO2 generation after addition of 0.5 mM DBCP and 81-98% inhibition with 3 mM DBCP, with all four substrates. The activities of alpha-ketoglutarate dehydrogenase, pyruvate dehydrogenase, malate dehydrogenase, and lactate dehydrogenase were not inhibited by DBCP. Since the DBCP-induced inhibition of metabolism of different substrates to CO2 was similar, and since DBCP did not inhibit enzyme activities of glycolysis or the TCA cycle, a common site of inhibition was suspected. In evaluations of mitochondrial electron transport chain activity, DBCP (3 mM) inhibited oxygen consumption resulting from metabolism of endogenous substrates plus alpha-ketoglutarate or malate by about 80%. When succinate, an FAD-dependent oxidation, was used as a substrate, oxygen consumption was not inhibited by DBCP. It is concluded that DBCP inhibits sperm carbohydrate metabolism at the NADH dehydrogenase step in the mitochondrial electron transport chain.
 ...
PMID:A biochemical basis for 1,2-dibromo-3-chloropropane-induced male infertility: inhibition of sperm mitochondrial electron transport activity. 367 26

Three anaesthetics (halothane, CF3CHClBr; Ethrane, F2 HCOF2CCHClF; cyclopropane) and one other halogenated, short-chain hydrocarbon (F-12, Cl2F2C) were tested under various conditions to determine their effects on the viability of cells of Escherichia coli and the activities of some of its enzymes. When any of the test chemicals were applied for 60 min at concentrations slightly in excess of saturation, the number of surviving cells decreased substantially, with halothane being the most biocidal of the four chemicals and F-12 the least. Three enzymes (malate dehydrogenase, MD; NADH dehydrogenase; glyceraldehyde-3-phosphate dehydrogenase, GPD) were tested for activity after treatment of E. coli with the test chemicals. In all instances, GPD was least resistant to inactivation and MD was most resistant. Halothane was most inhibitory followed in order by Ethrane, cyclopropane and F-12. Treatment of E. coli with halothane for 60 min at 23 degrees C and a concentration slightly in excess of saturation, resulted in nearly complete inhibition of all three enzymes.
 ...
PMID:Effect of anaesthetics and dichlorodifluoromethane on the viability of the cells of Escherichia coli and the activities of some of its enzymes. 391 44


1 2 3 4 5 6 7 8 9 Next >>