Spectroscopic evidence that salicylic acid converts a temporally inactivated form of horseradish peroxidase (compound III) to the irreversibly inactivated verdohemoprotein (P-670).

We obtained spectroscopic evidence in support of salicylate-dependent inactivation of horseradish peroxidase-C. Addition of salicylate to the enzyme arrested at a temporal inactive state (Compound III) in the presence of H2O2, resulted in rapid and irreversible inactivation of the enzyme yielding verdohemoproteins (P-670). Multiple roles for salicylate in peroxidase-catalyzed reactions are discussed.