About MDH

Malate Dehydrogenase (MDH)

Malate dehydrogenase (EC 1.1.1.37) is a redox family of enzymes that catalyze the oxidation of malate to oxalacetate with the concominant oxidation of NADH to NAD+ and H+ . The enzyme is thermodynamically favorable in the direction of OAA to Malate however in the mitochondria, physiological concentrations of OAA are so low to shift the delta Go' to favor the opposite direction. MDH is found in nearly all cells and in many with more than one isozyme present. In mammalian cells MDH is found in both the cytoplasm (MDH1 gene) and in the mitochondria (MDH2 gene) where the enzyme is involved in the Krebs Cycle, Gluconeogenesis and the Malate Aspartate Shuttle. In plants the enzyme is found in seed glycoxysomes (a specialized type of peroxisome) where MDH is involved in fatty acid metabolism as well as mitochondrial MDH (Citric Acid Cycle) while the cytoplasmic (soluble) isoform is involved in autotrophic carbon dioxide fixation and acid metabolism. Bacterial MDH plays the same role as plants in the TCA cycle and in many bacterial strains the enzyme is involved in electron transfer to modify quinones. While most reports show MDH to be a homodimer of 35,000 daltons for each subunit. There are reports of the enzyme acting as a monomer or even a tetramer.