Lactate dehydrogenase (LDH) is an enzyme that catalyzes the interconversion of pyruvate and lactate, playing a crucial role in anaerobic glycolysis and energy metabolism. It exists as five isoenzymes (LDH-1 to LDH-5), which are tetramers composed of different combinations of M and H subunits. LDH is widely expressed in various tissues, with different isoenzymes having distinct tissue distributions and functions. For instance, LDH-1 is abundant in the heart, while LDH-5 is prevalent in skeletal muscle and liver. In addition to its metabolic role, LDH is a biomarker for tissue damage, as its release into the bloodstream indicates cell injury or necrosis. Elevated LDH levels are commonly observed in conditions such as myocardial infarction, liver disease, and hemolysis. In cancer, LDH is involved in the Warburg effect, promoting tumor growth and survival by facilitating lactate production under hypoxic conditions. LDH also contributes to the acidic tumor microenvironment, which supports immune evasion and metastasis.
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