Mechanism of ligand binding to hemes and hemoproteins. A high-pressure study

Abstract

The effect of pressure on the recombination kinetics of small ligands binding to sperm whale myoglobin, protoheme dimethyl ester, and monochelated protoheme was studied with use of laser flash photolysis. The volumes of activation observed indicate that in both the protein and the models bond formation is the rate-determining step only for carbon monoxide, while for oxygen, isocyanides, and 1-methylimidazole almost no bond formation occurs in the transition state of the observed reaction. The effect of pressure on the escape of carbon monoxide, oxygen, and methyl isocyanide from the heme pocket of sperm whale myoglobin was also investigated