[Activity of the pyruvate dehydrogenase complex in Walker-256 carcinosarcoma]

Pyruvate dehydrogenase complex activity in the coarsely purified enzyme fractions (supernatant and mitochondrial extract) isolated from Walker-256 carcinosarcoma is shown to be much lower than the complex activity in the rat brain. Acetoin was not found in the incubation medium containing pyruvate dehydrogenase tumour complex. The rate of the reaction of nonoxidative formation of acetaldehyde by pyruvate dehydrogenase complex of the tumour was approximately five times lower than the rate of reaction catalyzed by the complex from the rat brain. It is shown that in the presence of adenine nucleotides AMP, ADP or ATP (0.5 mM) in the medium pyruvate: NAD+ oxidoreductase activity of the tumour complex is inhibited by 40-56% as compared to the control and reaction of nonoxidative decarboxylation of pyruvate is approximately 2 times activated. It is supposed that the accumulation of nonoxidative reaction products may be an essential factor for development and functioning of the tumour.