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 enzym es as a multi-enzyme complex may result in an alteration of the cataly tic properties of the enzymes present in this complex. This effect is not related to the channelling of reaction intermediates between diffe rent active sites. It appears as a consequence of an information trans fer that occurs within the multi-enzyme complex. A theory, based on st atistical thermodynamics, has been developed which provides an underst anding, 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 alter ation, through heterologous interactions, of an already existing co-op erativity of the oligomeric enzyme within the complex; a co-operativit y, generated by heterologous interactions in the complex that could no t occur if the oligomeric enzyme were isolated from the rest of the co mplex; a Michaelis-Menten character of the oligomeric enzyme within th e complex, but with altered values of V-m and K-m relative to what wou ld have been observed with the naked enzyme. All these effects appear as a consequence of a transfer of information between different enzyme s of the same multi-protein complex. The following paper in this journ al shows how one can demonstrate and characterize experimentally these effects in a multi-enzyme complex containing ribulose bisphosphate ca rboxylase-oxygenase.