Memory and imprinting in multienzyme complexes. Evidence for information transfer from glyceraldehyde-3-phosphate dehydrogenase to phosphoribulokinase under reduced state in Chlamydomonas reinhardtii.

The phosphoribulokinase, when it is in a reduced state in a bi-enzyme complex, is more active than when it is oxidized. This complex dissociates upon dilution to give a metastable reduced form of phosphoribulokinase, which differs from the stable form isolated beside the complex. The kinetic parameters of the reduced stable phosphoribulokinase and those of the complex are very similar, unlike those of the metastable form. Although the kinetic mechanism of the reduced stable form is ordered, with ribulose-5-phosphate binding first, ATP binds first to the phosphoribulokinase in the complex and to the metastable form. Therefore, phosphoribulokinase bears an imprint from glyceraldehyde-3-phosphate dehydrogenase after disruption of the complex. Dissociation of phosphoribulokinase from the complex also enhances its flexibility. The imprinting and greater flexibility result in the catalytic constant of dissociated phosphoribulokinase being 10-fold higher than that of the enzyme in the complex. Imprinting corresponds to stabilization-destabilization energies resulting from conformation changes generated by protein-protein interactions. The energy stored within the metastable phosphoribulokinase is mainly used to decrease the energy barrier to catalysis.