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The early history of research on peroxidase is most capably reviewed by Saunders et al (67). The first color reaction of biological material with guaiacum as substrate was noted in 1809, but the term peroxidase was used for the first time nearly a century later for an enzyme isolated from horseradish. In fact, peroxidase is widely distributed in the plant kingdom and also occurs in the animal kingdom. Many of the spectral aspects of this hemoprotein and its reaction products have been described in the above-mentioned text and elsewhere (e.g. 23). Different types of peroxidases were recognized, and an ever-increasing number of functions were ascribed to them, particularly in plant physiology (31). Therefore, while the basic chemical reactions of peroxidase (E. C . 1.1 1.1. 7) are well established, namely that of the peroxidatic cycle involving H202 and a large array of hydrogen donors (23), the questions of how its many isozymes function (31) and how its action in differentiation is controlled (68) remain largely unanswered. I do not review all publications on these topics here. A comprehensive tabulation has appeared recently (31). Instead, I offer a critical review of certain aspects of peroxidase in terms of structure and biosynthesis. |
