The Single Cysteinyl Residue (Cys341) of Carboxypeptidase Y for Cavity Control in the S1 Substrate Binding Pocket

摘要

Role of a single sulfhydryl group (Cys341) in carboxypeptidase Y (CPY) was investigated by combining site-directed mutagenesis and high-pressure techniques. triangle openV~not = in the CPY catalyzed hydrolysis of Fua-Phe-Phe and Fua-Ala-Phe and a computer simulation of the orientation of mutated residues led to an idea that Cys341 moves from inside to outside when the phenyl group in substrate P_1 site forms a transition state. Cys341 would play a role in controlling the size of the S1 substrate binding pocket so as to accept a large hydrophobic substrate by altering the cavity size of the pocket. Thus, the evaluation of the volume change by analyzing reaction kinetics under high presusre offers a useful method for microconformational change in protein.