Charge and molecular weight differences for fourteen guaiacol peroxidase isozymes in flax indicate that most are encoded by different structural genes

Abstract

Ferguson plots, linear regressions of log(relative mobility) against polyacrylamide gel concentration, provide an electrophoretic method of simultaneously obtaining estimates of net charge and molecular weight for nondenatured proteins, and are a powerful method of accurately comparing these characteristics among isozymes within an enzyme system. Here, Ferguson plots compare the characteristics of the nine isozymes (three cationic and six anionic) usually seen in soluble extracts of flax (Linum usitatissimum) seedling tissues, and of five anionic isozymes induced by heavy metal stress. Despite some differences in apparent molecular weight, all but one of the isozymes separated from each other on the basis of net charge and, except for a second isozyme with a comparatively high molecular weight, the net charges of the isozymes ranked in order of their relative mobilities on nondenaturing gels. Differences among the isozymes make it unlikely that any are related, which indicates that they are encoded by different structural genes.