H-1-NMR AND N-15-NMR STUDY OF THE BINDING OF THIOCYANATE TO CHEMICALLY-MODIFIED HORSERADISH-PEROXIDASE AND INVOLVEMENT OF SALT BRIDGE

The chemical modification of native horseradish peroxidase (HRP) has b een carried out by esterification of the heme propionic group. N-15- a nd H-1-NMR studies on binding of thiocyanate ion to chemically modifie d HRP have been utilized to demonstrate the existence of salt bridge b etween the heme propionic acid and distal amino acid group. The cataly zed oxidation of thiocyanate by the native HRP, and the chemically mod ified HRP has also been studied at different pH, and the significance of the salt bridge discussed.