Lactate Dehydrogenase and its Isoenzymes

Lactate dehydrogenase (EC 1.1.1.27; L-Lactate:NAD+ Oxidoreductase; LD)* belongs to the class of enzymes that catalyze oxidoreduction reactions and is widely distributed in all human tissues. It is involved in the last step of anaerobic glycolysis to regulate the pyruvate-lactate conversion for the replenishment of oxidized coenzyme, NAD+ (1–3). In the glycolytic pathway (Embden-Meyerhof), NAD+ is consumed with concomitant production of reduced nicotinamide adenine dinocleotide (NADH). LD catalyzes the of reduction of pyruvate to L-lactate with the mediation of NADH as a hydrogen donor. The reaction is reversible and strongly favors the production of lactate with an equilibrium constant of 3.6 × 104 M-l (4)