PKM and cancer: Recent studies have shown that pyruvate kinase, the enzyme that catalyzes the last step of glycolysis (phosphoenolpyruvate conversion to pyruvate),[7] functions as a regulator of cancer cell metabolism, which is exemplified high glucose consumption and lactate production.[15] There are four isoforms of pyruvate kinase in mammalian cells (PKR, PKL, PKM1, PKM2).[16] While PKM1 is expressed in skeletal muscle, heart and brain, the PKM2 isoform is expressed in embryonic development and is almost universally re-expressed in cancer cells.[9, 17] Unlike PKM1, PKM2 mainly promotes aerobic glycolysis.