Pyruvate kinase is a key enzyme in the glycolytic pathway. The M2 isoenzyme of pyruvate kinase is specifically expressed at high levels in tumor cells, and can be measured in plasma of patients with advanced breast cancer. The marker is useful for measuring disease activity, sensitivity to chemotherapy and recurrence Synonyms: Pyruvate kinase isozymes M1/M2, EC 2.7.1.40, Pyruvate kinase muscle isozyme, Pyruvate kinase 2/3, Cytosolic thyroid hormone-binding protein, CTHBP, THBP1, M2PK, PKM2, PK3, PK2, PKM, TCB, OIP3, MGC3932, Tumor .