Immunochemical relatedness of two peroxidase isozymes from peanut cell culture

Abstract

The immunological relationships between a cationic and an anionic peroxidase from peanut cell suspension culture were probed with polyclonal antibodies raised against each and with a monoclonal antibody raised against the cationic isozyme. Partial identity of the two isozymes was established by cross-reactivities of the polyclonal antibodies directed to one peroxidase with the alternate isozyme. Some peptides from Western blots of the partially hydrolysed peroxidases were recognized by both antisera, even though the peptide maps of the two isozymes differed. In contrast, the monoclonal antibody reacted more specifically to the fragments derived from the cationic isozyme. The anti-anionic peroxidase serum was passed over a cationic peroxidase (C.PRX) – Sepharose affinity column to separate antibodies cross-reacting with C.PRX from those specific to the anionic isozyme. Deglycosylation of the cationic and the anionic peroxidases eliminated binding of the antibody fraction eluted from the C.PRX–Sepharose column to the deglycosylated forms of peroxidases. These data suggest (i) that complex structural relationships exist between the cationic and the anionic peanut peroxidases, (ii) that the carbohydrate moieties of the two isozymes are antigenically similar to each other, and (iii) that epitope mapping will help in characterizing further each isoperoxidase.Key words: peroxidase, isozymes, ELISA, immunoblotting, peptide mapping.