title: Synergistic effect of ammonium and potassium ions on pyruvate kinase from Ehrlich ascites tumor cells.
abstract: The effect of NH4+ on M2-pyruvate kinase isolated from Ehrlich ascites tumor cells was investigated. The enzyme is activated by NH4+ more efficiently than by K+. Moreover, a synergistic interaction of the two cations is observed since NH4+ increases the affinity of the enzyme for K+. The affinity of the enzyme for phosphoenolpyruvate is also increased in the presence of NH4+, and in these conditions the activating effect of fructose-1,6-bisphosphate is reduced. It is proposed that NH4+ be considered a specific allosteric activator of the tumor enzyme.
mesh_terms: D000641:Ammonia / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D002286:Carcinoma, Ehrlich Tumor / Q000201:enzymology; D004357:Drug Synergism; D004789:Enzyme Activation; D007700:Kinetics; D051379:Mice; D010728:Phosphoenolpyruvate / Q000378:metabolism; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D011770:Pyruvate Kinase / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D010728:Phosphoenolpyruvate; D000641:Ammonia; D011770:Pyruvate Kinase; D011188:Potassium