A CRITICAL ROLE OF PROTEIN-BOUND WATER IN THE CATALYTIC CYCLE OF CYTOCHROME-P-450 CAMPHOR

The rates of NADH oxidation during the hydroxylation of camphor by cytochrome P-450cam were followed in the presence of co-solvents used to increase the osmotic pressure surrounding the protein-bound water. As a result, the measured V(max) decreases independently of the perturbant tested. Roughly 28 molecules of water, involved during the catalytic cycle, are deduced from the variation of V(max) as a function of osmotic pressure. These molecules, in part, could be those present in the cytochrome P-450cam-putidaredoxin interface.