SUBSTRATE-INDUCED ENZYME DIMERIZATION - KINETICS OF ONE-SUBSTRATE AND2-SUBSTRATE REACTIONS

The catalytic activity of many oligomeric enzymes is regulated by asso ciation-dissociation processes, We studied kinetic models for mono-and bisubstrate reactions involving a catalytically active dimeric form o f apr enzyme induced by its interaction with substrate. The concentrat ion dependences of the reaction rate are different in these two cases; they also differ from the dependences predicted by the Michaelis sche mes. For instance, the rate dependence on enzyme concentration proves to be nonlinear. The models also predict inhibition at higher substrat e concentrations; however, a model can be put forward in which one of the two substrates is not inhibitory, For multisubstrate reactions req uiring substrate-induced enzyme dimerization, the order of substrate b inding to enzyme can be established by routine inhibitor analysis usin g various substrate analogs, as with enzymic systems exhibiting linear concentration dependences. An important point is that discrimination of the reaction models may only be effective if the reaction rates are measured over a wide range of enzyme/substrate concentrations.