PLANT PEROXIDASES - AN ORGANISMIC PERSPECTIVE

Peroxidases are ubiquitous enzymes found in virtually all green plants, many fungi and aerobic bacteria. The isozymic heterogeneity of peroxidases appears to result from de novo synthesis, as well as an array of physiological/ecological determinants including hormones, light, gravity, and infection. Homologies among isoperoxidases from the same species are largely distinguished by the isoelectric point and as well as by protein sequence data. The basic and acidic peroxidases from a number of angiosperms show a greater functional and structural relationship within rather than between these groups. Peroxidases have phylogenetically-correlated similarities based on the chemical nature and redox potentials of the substrates which they can oxidize. Peroxidases often increase as a response to stress, and one of the principle roles of peroxidase appears to be cellular protection from oxidative reactions imposed on all photosynthetic plants. The relationships among the peroxidases, IAA and lignification emerge as a particular adaptation of vascular plants to the land environment. The great catalytic versatility of peroxidase as its predominant character and, therefore, no single major role need necessarily exist for this multifaceted enzyme.