THE MODULATION OF ENZYME REACTION-RATES WITHIN MULTIENZYME COMPLEXES .1. STATISTICAL THERMODYNAMICS OF INFORMATION-TRANSFER THROUGH MULTIENZYME COMPLEXES

There is now experimental evidence that association of different enzymes as a multi-enzyme complex may result in an alteration of the catalytic properties of the enzymes present in this complex. This effect is not related to the channelling of reaction intermediates between different active sites. It appears as a consequence of an information transfer that occurs within the multi-enzyme complex. A theory, based on statistical thermodynamics, has been developed which provides an understanding, on a physical basis, for how isologous as well as heterologous interactions between identical, or different, enzymes of the complex may modulate the catalytic properties of an oligomeric enzyme of that complex. The theory predicts three possible types of effects: an alteration, through heterologous interactions, of an already existing co-operativity of the oligomeric enzyme within the complex; a co-operativity, generated by heterologous interactions in the complex that could not occur if the oligomeric enzyme were isolated from the rest of the complex; a Michaelis-Menten character of the oligomeric enzyme within the complex, but with altered values of V-m and K-m relative to what would have been observed with the naked enzyme. All these effects appear as a consequence of a transfer of information between different enzymes of the same multi-protein complex. The following paper in this journal shows how one can demonstrate and characterize experimentally these effects in a multi-enzyme complex containing ribulose bisphosphate carboxylase-oxygenase.