Abstract
Physicochemical and enzymatic properties of five purified isoenzymes of Japanese-radish peroxidase were investigated comparatively. The molecular weight of peroxidase was different among the acidic, neutral and basic isoenzymes, while the ordered secondary structures seemed to be essentially the same on the observation of infrared spectra. The acidic isoenzyme, No. 3, exhibited a characteristic behavior in the visible absorption spectrum, which showed a thermal interconversion between high- and low-spin states at low temperatures and also the lowest pK value of the proton dissociation to form the hydroxide compound. The basic isoenzyme, No. 16, was characteristic in its highest affinity for cyanide. In the catalytic activity, the weakly acidic isoenzyme No. 5 was the most active, exhibiting the highest rate constants both for hydrogen peroxide and for guaiacol.
