Lactate dehydrogenase (LDH) catalyzes the interconversion of pyruvate and NADH to lactate and NAD+. When the oxygen supply is too low for mitochondrial ATP production, this reaction recycles NADH generated in glycolysis to NAD+, which reenters glycolysis. The major form of LDH found in muscle cells is the A (LDHA) isozyme.
