SUBSTRATE ACTIVATION OF PYRUVATE CARBOXYLASE BY PYRUVATE

A kinetic analysis of pyruvate carboxylase isolated from sheep liver and using pyruvate as the variable substrate revealed non-Michaelis Menten kinetic. Double reciprocal plots were biphasic and RS values of 222 were obtained. Hill plots prepared from the initial velocity data showed that at low pyruvate concentrations, the slope of the line varied from 1.0 to 0.7 and then decreased to 0.4 at 0.8 × 10-3M-pyruvate. With increasing pyruvate concentrations, the slope increased to a value of 1.0. This type of kinetic behaviour is typical of a system in which there is negative cooperativity with respect to ligand binding with concurrent progressive substrate activation. © 1969.