Evidence for heterogeneity in the carbohydrate moieties of peroxidase isozymes from two environmentally induced flax genotrophs

Abstract

The corresponding isoperoxidases from the flax genotrophs L and S have different molecular weights. Utilizing affinity chromatography on Sepharose-bound concanavalin A, we have shown that this lectin has a stronger affinity for the isoperoxidases purified from S stem tissue than those from L. The presence of differences in the carbohydrate composition of L and S peroxidases was confirmed when it was observed that only S peroxidases were susceptible to digestion by endo-β-N-acetylglucosaminidase H. Glycoprotein-enriched fractions were then purified from L and S stem tissue. The results showed that most glycoproteins of S origin have higher molecular weights than their L counterparts. Certain glycoproteins were digested by endo-β-N-acetylglucosaminidase H only if they were of S origin, while others were digested regardless of their origin. In both cases, the original differences in molecular weight between L and S glycoproteins were eliminated. These results support our view that posttranslational modification at the level of the carbohydrate chains of the L and S peroxidases is the reason for their heterogeneity on polyacrylamide gels.