Kinetic analysis of cooperativity of phosphorylated L-type pyruvate kinase

Kinetics of L-type pyruvate kinase (EC 2.7.1.40) catalysed reaction between phosphoenolpyruvate (PEP) and ADP was analysed under steady-state conditions and the interac- tion of both substrates with the enzyme was characterized proceeding from bi-substrate kinetic mechanism of this process. Cooperative regulation of the rate of this process by one of the substrates, PEP, was taken into consideration by using a sequential ligand binding model. It was found that two PEP molecules may bind with similar affinity with the tetrameric enzyme (3 0 mM), K = while the effectiveness of the binding of the next two substrate molecules is enhanced through cooperative interaction between the enzyme subunits, which decreases the dissociation constant of the enzyme-substrate complex approximately 10 times.