Pyruvate Kinase

Pyruvate kinase is an enzyme that catalyzes the conversion of phosphoenolpyruvate and ADP to pyruvate and ATP in glycolysis and plays a role in regulating cell metabolism. There are four mammalian pyruvate kinase isoforms with unique tissue expression patterns and regulatory properties. Pyruvate kinase has four different tissue-specific isozymes in animals, PKL, PKR, PKM1, and PKM2. The L and R isozymes are expressed in the liver (L) and red blood cells (R), whereas PKM2 is expressed in early embryonic cells and other proliferating cells, and PKM1 is expressed in the brain, skeletal muscle, and heart which need high energy.

PKM1 and PKM2 are formed by a single mRNA transcript of the PKM gene by alternative splicing. The oligomers of PKM2 exist in high activity tetramer and low activity dimer forms. The dimer PKM2 regulates the rate-limiting step of glycolysis that shifts the glucose metabolism from the normal respiratory chain to lactate production in tumor cells. Besides its role as a metabolic regulator, it also acts as a protein kinase, which contributes to tumorigenesis. PKM2 serves as a promising target for cancer treatment.