Lactate dehydrogenase (LDH) is an ubiquitous enzyme commonly found in wide variety of organisms, including plants and microbes. LDH is involved in the interconversion of the pyruvate and NADH to lactate and NAD+. It is also called Hydroxybutyrate Dehydrogenase (HBD), because it can catalyze the oxidation of hydroxybutyrate (1). In mammals, three types of LDH subunits (35 kDa) are encoded by the genes Ldh-A, Ldh-B, and Ldh-C. All LDH subunits can combine to form various terameric isoenzymes (140 kDa) (2). LDHA and LDHB are expressed in most somatic tissues, while expression of LDHC is confined to the germinal epithelium of the testes (3)
