<p>This family contains both lactate and malate dehydrogenases. Malate dehydrogenases catalyse the interconversion of malate to oxaloacetate. The enzyme participates in the citric acid cycle.</p><p>L-lactate dehydrogenase (<db_xref db="EC" dbkey="1.1.1.27"/>) (LDH) [<cite idref="PUB00003226"/>] catalyses the reversible NAD-dependent interconversion of pyruvate to L-lactate. In vertebrate muscles and in lactic acid bacteria it represents the final step in anaerobic glycolysis. This tetrameric enzyme is present in prokaryotic and eukaryotic organisms. In vertebrates there are three isozymes of LDH: the M form (LDH-A), found predominantly in muscle tissues; the H form (LDH-B), found in heart muscle and the X form (LDH-C), found only in the spermatozoa of mammals and birds. In birds and crocodilian eye lenses, LDH-B serves as a structural protein and is known as epsilon-crystallin [<cite idref="PUB00004665"/>].</p><p>L-2-hydroxyisocaproate dehydrogenase (<db_xref db="EC" dbkey="1.1.1"/>) (L-hicDH) [<cite idref="PUB00001780"/>] catalyses the reversible and stereospecific interconversion between 2-ketocarboxylic acids and L-2-hydroxy-carboxylic acids. L-hicDH is evolutionary related to LDH's.</p>