NONCOVALENT AND REVERSIBLE IMMOBILIZATION OF CHEMICALLY-MODIFIED AMYLOGLUCOSIDASE AND BETA-GLUCOSIDASE ON DEAE-CELLULOSE

The acylation of amino groups of proteins by pyromellitic dianhydride (PMDA) leads to an increase in negative charges on the protein surface by 4 units for every amino group modified. This reaction has been use d to modify enzymes for the purpose of adsorption on DEAE-cellulose. T he 49% amino groups of amyloglucosidase were modified with 90% residua l enzyme activity. Whereas the native enzyme bound to DEAE-cellulose a nd could be eluted out with 0.1 M sodium chloride, the modified enzyme exhibited stronger binding and could only be eluted with 0.25 M sodiu m chloride. In the case of adsorbed native enzyme, heating at 60-degre es-C for 1 h led to desorption of 97% protein. In the case of the modi fied enzyme, the immobilized preparation retained full enzyme activity under similar conditions. beta-Glucosidase (which did not bind to DEA E-cellulose) upon modification with PMDA was found to bind to DEAE-cel lulose and could be eluted out with 97% protein recovery by washing wi th O.2 M sodium chloride. Thus, chemical modification with PMDA may be a useful and general strategy for obtaining enzyme derivatives for re versible adsorption on anion exchangers.