Broad-line nuclear magnetic resonance studies of chloroperoxidase

Abstract

Chloroperoxidase, a heme glycoprotein isolated from the mold Caldariomyces fumago, was studied by NMR relaxation techniques. Interaction of the chloride ion substrate with the enzyme may be analyzed as consisting of at least 3 contributions: a weak interaction with the Fe atom, nonspecific anion-protein interactions, and a specific interaction generated at low pH. The data indicate that a specific interaction, which develops in parallel with enzyme activity at low pH, does not occur at the Fe atom 1st coordination sphere site. The results are summarized in terms of an enzymatic mechanism not involving Cl ion coordination to the Fe atom.