LDHB, also known as L-lactate dehydrogenase B chain, is a member of the lactate dehydrogenase family. It is an oxidoreductase which catalyses the interconversion of pyruvate and lactate with concomitant interconversion of NADH and NAD+. As this protein can also catalyze the oxidation of hydroxybutyrate, it is occasionally called Hydroxybutyrate Dehydrogenase (HBD). The LDH family consists of three members, LDH-A, LDH-B and LDH-C. LDHs function as powerful markers for germ cell tumors.