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

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.
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PMID:Direct demonstration of enol-oxaloacetate as an immediate product of malate oxidation by the mammalian succinate dehydrogenase. 186 83

Pea leaf mitochondria showed complex kinetics for malate metabolism. O2 uptake increased as malate concentration increased from 0 to 10 mM, reached a plateau between 10 and 20 mM malate, and then increased again up to 40 mM malate. Analysis of the products of malate oxidation by high-performance liquid chromatography revealed that the first phase of O2 uptake coincided with the synthesis of both pyruvate and oxalacetate (OAA) while the second phase of O2 uptake at higher malate levels usually occurred with a large increase in OAA formation. The biphasic response in O2 uptake and the changing ratios of pyruvate and OAA synthesis did not appear to be the direct result of the differing Km values of malate dehydrogenase and malic enzyme. Rather, they resulted from thermodynamic properties of these two malate oxidases and the kinetics of the two NADH dehydrogenases found in plant mitochondria. At low malate concentrations the rotenone-sensitive NADH dehydrogenase was active and could accept electrons from both malate oxidases. This NADH dehydrogenase became saturated at about 10 mM malate. At higher malate concentrations the rotenone-insensitive NADH dehydrogenase was increasingly important and its increased electron transport capacity was best exploited by malate dehydrogenase. At the higher malate concentrations an increasing portion of the electrons from malate reduce O2 through the alternative oxidase. Although this coincided with the second phase of malate-dependent O2 uptake it was not required for this phase to be seen.
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PMID:Changes in the electron transport chain of pea leaf mitochondria metabolizing malate. 662 11