The malate dehydrogenase (abbreviated to MDH) is an enzyme in the citric acid cycle that catalyzes the conversion of malate into oxal acetate (using NAD) and vice versa (this is a reversible reaction). Malate dehydrogenase should not be confused with the same decarboxylating enzyme malate dehydrogenase, which catalyzes the conversion of malate to pyruvate, with NADP consumption. Biochemical functions
Malate dehydrogenase is also involved in gluconeogenesis, the synthesis of glucose from smaller molecules. Pyruvate in the mitochondria is converted into oxal acetate by the pyruvate carboxylase, an intermediate in the citric acid cycle. To transport the oxalacetate from the mitochondria, it is reduced to malate by malate dehydrogenase. This malate can easily pass the inner mitochondral membrane. Once the malate is in the cytosol, the malate dehydrogenase oxidizes again to oxalic acetate. Eventually, the oxal acetate is converted to phosphoenolpyruvate by phosphoenolpyruvate carboxykinase.
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