Carbohydrate metabolism in neoplastic tissue

The kinetic and immunological properties of purified, homogeneous pyruvate kinase type M2 from chicken lung and tumors, including that of Rous sarcoma virus transformed chicken fibroblasts, have been compared. The type M2 enzymes from both lung and tumors have immunologically distinct structures. The enzyme isolated from tumors is characterized by a low affinity for phosphoenol pyruvate, pronounced L-serine activation and a strong inhibition by L-alanine, L-proline and several other amino acids. The chicken lung enzyme is only slightly affected by serine. The cellular amino acid concentration is in such a range that the tumor enzyme is strongly inhibited whereas the lung enzyme is only partially inhibited. The characteristics of the tumor enzyme allow the optimal adaptation to lactic acid and production of energy from glucose or amino acids dependent on substrate and oxygen supply.