A flavoprotein (FAD). Vitamin K and several other quinones can act as acceptors. Different from EC 1.1.1.37 (malate dehydrogenase (NAD+)), EC 1.1.1.82 (malate dehydrogenase (NADP+)) and EC 1.1.1.299 (malate dehydrogenase [NAD(P)+]).
The taxonomic range for the selected organisms is: Corynebacterium glutamicum The expected taxonomic range for this enzyme is: Bacteria, Eukaryota, Archaea
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SYSTEMATIC NAME
IUBMB Comments
(S)-malate:quinone oxidoreductase
A flavoprotein (FAD). Vitamin K and several other quinones can act as acceptors. Different from EC 1.1.1.37 (malate dehydrogenase (NAD+)), EC 1.1.1.82 (malate dehydrogenase (NADP+)) and EC 1.1.1.299 (malate dehydrogenase [NAD(P)+]).
the enzyme takes part in the citric acid cycle. It oxidizes L-malate to oxaloacetate and donates electrons to ubiquinone-1 and other artificial acceptors or, via the electron transfer chain, to oxygen. NAD is not an acceptor and the natural direct acceptor for the enzyme is most likely a quinone. A mutant completely lacking Mqo activity grows poorly on several substrates tested. This enzyme might be especially important when a net flux from malate to oxaloacetate is required, but the intracellular concentrations of the reactants are unfavourable for the NAD-dependent reaction (EC 1.1.1.37)
Corynebacterium glutamicum possesses two types of L-malate dehydrogenase, a membrane-associated malate:quinone oxidoreductase (MQO) and a cytoplasmic malate dehydrogenase (MDH, EC 1.1.1.37). MQO, MDH, and succinate dehydrogenase (SDH) activities are regulated coordinately in response to the carbon and energy source for growth. Compared to growth on glucose, these activities are increased during growth on lactate, pyruvate, or acetate, substrates which require high citric acid cycle activity to sustain growth. MQO is the most important malate dehydrogenase in the physiology of Corynebacterium glutamicum. A mutant with a site-directed deletion in the mqo gene does not grow on minimal medium. Growth can be partially restored in this mutant by addition of the vitamin nicotinamide. In contrast, a double mutant lacking MQO and MDH does not grow even in the presence of nicotinamide. MDH is able to take over the function of MQO in an mqo mutant, but this requires the presence of nicotinamide in the growth medium. It is shown that addition of nicotinamide leads to a higher intracellular pyridine nucleotide concentration, which probably enables MDH to catalyze malate oxidation. Purified MDH catalyzes oxaloacetate reduction much more readily than malate oxidation at physiological pH. In a reconstituted system with isolated membranes and purified MDH, MQO and MDH catalyze the cyclic conversion of malate and oxaloacetate, leading to a net oxidation of NADH. Evidence is presented that this cyclic reaction also takes place in vivo
the loss of malate:quinone oxidoreductase activity down-regulates the flux of the tricarboxylic acid cycle to maintain the redox balance and results in redirection of oxaloacetate into L-lysine biosynthesis
the enzyme takes part in the citric acid cycle. It oxidizes L-malate to oxaloacetate and donates electrons to ubiquinone-1 and other artificial acceptors or, via the electron transfer chain, to oxygen. NAD is not an acceptor and the natural direct acceptor for the enzyme is most likely a quinone. A mutant completely lacking Mqo activity grows poorly on several substrates tested. This enzyme might be especially important when a net flux from malate to oxaloacetate is required, but the intracellular concentrations of the reactants are unfavourable for the NAD-dependent reaction (EC 1.1.1.37)
Corynebacterium glutamicum possesses two types of L-malate dehydrogenase, a membrane-associated malate:quinone oxidoreductase (MQO) and a cytoplasmic malate dehydrogenase (MDH, EC 1.1.1.37). MQO, MDH, and succinate dehydrogenase (SDH) activities are regulated coordinately in response to the carbon and energy source for growth. Compared to growth on glucose, these activities are increased during growth on lactate, pyruvate, or acetate, substrates which require high citric acid cycle activity to sustain growth. MQO is the most important malate dehydrogenase in the physiology of Corynebacterium glutamicum. A mutant with a site-directed deletion in the mqo gene does not grow on minimal medium. Growth can be partially restored in this mutant by addition of the vitamin nicotinamide. In contrast, a double mutant lacking MQO and MDH does not grow even in the presence of nicotinamide. MDH is able to take over the function of MQO in an mqo mutant, but this requires the presence of nicotinamide in the growth medium. It is shown that addition of nicotinamide leads to a higher intracellular pyridine nucleotide concentration, which probably enables MDH to catalyze malate oxidation. Purified MDH catalyzes oxaloacetate reduction much more readily than malate oxidation at physiological pH. In a reconstituted system with isolated membranes and purified MDH, MQO and MDH catalyze the cyclic conversion of malate and oxaloacetate, leading to a net oxidation of NADH. Evidence is presented that this cyclic reaction also takes place in vivo
the loss of malate:quinone oxidoreductase activity down-regulates the flux of the tricarboxylic acid cycle to maintain the redox balance and results in redirection of oxaloacetate into L-lysine biosynthesis
reduction of 2,6-dichlorophenol indophenol by solubilized enzyme is activated significantly by addition of the quinones decylubiquinone, duroquinone, 2-methyl-1,4-naphthoquinone (vitamin K3), ubiquinone-0 and ubiquinone-1. Optimal activation is observed with ubiquinone-1
reduction of 2,6-dichlorophenol indophenol by solubilized enzyme is activated significantly by addition of the quinones decylubiquinone, duroquinone, 2-methyl-1,4-naphthoquinone (vitamin K3), ubiquinone-0 and ubiquinone-1. Optimal activation is observed with ubiquinone-1
reduction of 2,6-dichlorophenol indophenol by solubilized enzyme is activated significantly by addition of the quinones decylubiquinone, duroquinone, 2-methyl-1,4-naphthoquinone (vitamin K3), ubiquinone-0 and ubiquinone-1. Optimal activation is observed with ubiquinone-1
reduction of 2,6-dichlorophenol indophenol by solubilized enzyme is activated significantly by addition of the quinones decylubiquinone, duroquinone, 2-methyl-1,4-naphthoquinone (vitamin K3), ubiquinone-0 and ubiquinone-1. Optimal activation is observed with ubiquinone-1
reduction of 2,6-dichlorophenol indophenol by solubilized enzyme is activated significantly by addition of the quinones decylubiquinone, duroquinone, 2-methyl-1,4-naphthoquinone (vitamin K3), ubiquinone-0 and ubiquinone-1. Optimal activation is observed with ubiquinone-1
when stored on ice, the half-life is approximately 120 h, important stabilizing conditions for storage on ice are the presence of EDTA and EGTA. the presence of glycerol, and pH 6. The presence of Mg2+ and Ca2+ has a destabilizing effect
the disruption of the mqo gene results in increased L-lysine production. The mutation supports industrial levels of L-lysine production in Corynebacterium glutamicum