ATP inhibition of Phycomyces pyruvate kinase: a kinetic study of the inhibitory effects on the allosteric kinetics shown by the enzyme.

Studies on ATP effects on the allosteric kinetics shown by pyruvate kinase from Phycomyces blakesleeanus NRRL 1555 (-) are reported. Phosphoenolpyruvate showed an allosteric ATP-dependent substrate inhibition. The results supported the existence of spatially distinct catalytic binding sites and the inhibitory binding sites for phosphoenolpyruvate, and ATP showed opposite heterotropic effects with respect to these two types of binding site. With respect to Mg2+ ions, ATP caused a negative heterotropic effect. The global inhibitory effect of ATP was in agreement with the predictions postulated by the two-state concerted-symmetry model of Monod, Wyman and Changeux.