Jake Ezell Sandbox 3

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Malate Dehydrogenase

Malate Dehydrogenase (MDH)(PDB entry 2x0i) is most known for its role in the metabolic pathway in the tricarboxylic acid cycle[1]; however, the enzyme is also in many other metabolic pathways such as glyoxylate bypass, amino acid synthesis, glucogenesis, and oxidation/reduction balance ^[1]. It is classified as a oxidoreductase[2]. Malate Dehydrogenase has been extensively studied due to its many isozymes ^[2]. The enzyme exists in two places inside a cell, in the mitochondria and cytoplasm. In the mitochondria, the enzyme catalyzes the reaction of malate to oxaloacetate; but in the cytoplasm, the enzyme catalyzes oxaloacetate to malate to allow transport ^[3]. This conversion is an essential catalytic step in each different metabolic mechanism. The enzyme malate dehydrogenase is composed of either a dimer or tetramer ^[4].

The evolutionary past of MDH shows a divergence to form lactate dehydrogenase (LDH) which functions in a very similar way to MDH. Although there is a very low sequence conservation among MDH and LDH’s [3] the structure of the enzyme has remained relatively conserved. The key difference between the two is in the substrate: LDH catalyzes pyruvate to lactate.