Lactate dehydrogenase (LDH) is an oxidoreductase. LDH catalyzes the conversion of lactate to pyruvic acid and back, as it converts NAD+ to NADH and back. LDH is composed of four subunits (tetramer). The two most common subunits are the LDH-M and LDH-H protein. LDH is released into the blood by cells after tissue damage or erythrocyte hemolysis. Extracellular LDH activity is used to detect cell damage or cell death
