Study of cytochrome oxidase co-binding site using low-temperature flash photolysis

Flash photolysis has been used to study the kinetics of CO-binding to the heme alpha isolated cytochrome oxidase. Experiments performed over the range 185-295 degrees K with various CO concentrations have revealed significant deviations from the Arrhenius relationship between rate and temperature. These findings can be explained by a model in which the heme site is considered to have three regions between which CO can move; only from the innermost one can binding to the heme iron take place. The relative enthalpies and entropies of the three regions are calculated.