The conversion of horseradish peroxidase C to a verdohemoprotein by a hydroperoxide derived enzymatically from indole-3-acetic acid and by m-nitroperoxybenzoic acid.

A verdohemoprotein was formed from Compound I of horseradish peroxidase C upon the addition of about 2 molar equivalents of m-nitroperoxybenzoic acid (mNPBA) or hydroperoxide formed from indole-3-acetic acid during its catalytic oxidation. The formation of the verdohemoprotein occurred via two intermediates which have an absorbance peak at 965 or 940 nm. Carbon monoxide was evolved in the reaction from the 940 compound to the verdohemoprotein. From the kinetic and titration data, the following reaction sequence was proposed. (Formula: see text). The 940 compound could be reduced by dithionite and ascorbate to the ferrous and the ferric enzyme, respectively. The enzyme species that reacted with mNPBA to form the 965 and the 940 compounds was concluded to be Compound I but neither Compound II nor oxyperoxidase (Compound III).