Structural and kinetic differences between the M2 type pyruvate kinases from lung and various tumors.

The kinetic and structural properties of purified, homogeneous pyruvate kinase type M2 from chicken lung and tumors, including that from Rous sarcoma virus-transformed chicken fibroblasts, have been compared. The "tumor enzyme" is characterized by a low affinity for phosphoenolpyruvate, pronounced serine activation, and strong alanine inhibition as compared to the "lung type". In contrast to the rat lung enzyme, which is not affected by serine, the chicken lung enzyme is slightly activated by serine. The serine metabolites phosphoserine and glycine do not activate the "tumor type M2 pyruvate kinase", but L-alpha-glycerophosphorylcholine and phosphatidylserine do slightly activate at physiological concentrations. Studies with substances structurally related to serine reveal that the hydroxyl group of serine is a prerequisite for the activation and that the amino and carboxyl groups determine the affinity of the "tumor type M2 pyruvate kinase" for serine. Two different fragmentation methods (CNBr-cleavage and V-8 proteolysis) and two different methods for separation of the resulting peptide fragments (polyacrylamide gel isoelectric focussing and SDS-polyacrylamide electrophoresis) indicated a high degree of homology between the type M2 pyruvate kinases from lung and tumors as well the type M1 from muscle. Each type of pyruvate kinase, however, contains one or two unique protein fragments which are characteristic for its type. We have termed those fragments L (lung), M (muscle), and T (tumor).