Information Transfer in Multienzyme Complexes

Oxidized phosphoribulokinase is almost inactive in its isolated state but becomes active when associated with glyceraldehyde‐3‐phosphate dehydrogenase. There is therefore an information transfer that takes place between these two enzymes. However, when the complex dissociates, free oxidized phosphoribulokinase is even more active than when it is associated with glyceraldehyde‐3‐phosphate dehydrogenase. This means that glyceraldehyde‐3‐phosphate dehydrogenase exerts an imprinting effect upon phosphoribulokinase which persists for a while after the parting of the two proteins.Various methods derived from statistical thermodynamics can be used to estimate the fraction of energy transferred from glyceraldehyde‐3‐phosphate dehydrogenase to phosphoribulokinase and which alters the kinetic parameters of the latter enzyme. In the complex, the decrease of the free energy associated with the binding of ribulose 5‐phosphate is larger than that of ATP. This implies that the mutual association of the two enzymes facilitates the binding of the former substrate but is without effect on that of the latter. The main effect exerted by the association of the two enzymes is to decrease by about 10 kJ/