PKM2 (EC 126.96.36.199) is an isoenzyme of the glycolytic enzyme pyruvate kinase. Four isoforms of pyruvate kinase have been characterized: the L (PKL) and R (PKR) isoforms, and the M1 (PKM1) and M2 (PKM2) isoforms. The M2 isoform of catalyzes the final and also a rate-limiting reaction in the glycolytic pathway. The less active form of PKM2 drives glucose through the route of aerobic glycolysis, while active PKM2 directs glucose towards oxidative metabolism. Additionally, PKM2 possesses protein tyrosine kinase activity and plays a role in modulating gene expression and thereby contributing to tumorigenesis. Since all tumor cells exclusively express the embryonic M2 isoform of PK, it is hypothesized that PKM2 is a potential target for cancer therapy. Modulation of PKM2 might also be effective in the treatment of obesity, diabetes, autoimmune conditions, and antiproliferation-dependent diseases.
 N. Wong et al. PKM2, a Central Point of Regulation in Cancer Metabolism. Int. J. Cell Biol. 2013, 2013, 242513.