Time-Dependent Enzyme Activity Dominated by Dissociation of J-Aggregates Bound to Protein Surface

J-Aggregates of diprotonated 5,10,15,20-tetrakis(4-sulfonatopheny)porphyrin (H4TPPS2-) were stabilized even in a neutral aqueous solution (pH 7.0) containing per-O-rnethylated beta-cyclodextrin by binding to the surface of a-chymotrypsin (ChT). The large J-aggregates covered the active site of ChT and completely inhibited the hydrolysis of the peptides. However, enzyme activity was gradually restored with the dissociation of the J-aggregates attached to the protein surface to monomers. After the completion of dissociation of the aggregates, the enzyme activity was almost completely restored, though the structure of ChT significantly changed. Circular dichroism spectroscopy suggested that the microscopic structure at the active site of ChT was scarcely affected by the J-aggregates, hut the binding of J-aggregates to ChT increased the content of the random coils in the enzyme. The present study showed a new type of effector for controlling the function of ChT.