Pyruvate Kinase Isozymes R/L (PKLR) belongs to the pyruvate kinase family, There are 4 isozymes of pyruvate kinase in mammals: L, R, M1 and M2. L type is major isozyme in the liver; R is found in red cells; M1 is the main form in muscle, heart and brain; M2 is found in early fetal tissues. PKLR exists as a homotetramer and catalyzes the production of phosphoenolpyruvate from pyruvate and ATP. Defects in PKLR are also the cause of pyruvate kinase deficiency of red cells, which is a frequent cause of hereditary non-spherocytic hemolytic anemia.