Lactate Dehydrogenase

Lactate dehydrogenase (LDH) catalyzes the reaction below. This reaction provides an important source of NAD+ for cells undergoing anaerobic glycolysis.

> Pyruvate + NADH + H+ <=> Lactate + NAD+

LDH is a tetrameric protein consisting of two types of subunits, called M and H, which have small differences in amino acid sequence. Different molecular forms of an enzyme are called isoenzymes or isozymes. M subunits predominate in skeletal muscle and liver, and H subunits predominate in heart. M and H subunits combine randomly with each other, so that the five major isoenzymes have the compositions M 4, M 3 H, M 2H 2, MH 3, and H 4. Because of random subunit reassortment, the isoenzymic composition of a tissue is determined primarily by the activities of the genes specifying the two subunits.

See also: LDH Isoenzymes, Pyruvate/Lactate/Ethanol Metabolism, Anaerobic Process for Generating Metabolic Energy, Lactic Acid Fermentation, Ethanol Metabolism and Gluconeogenesis