REVERSIBLE IMMOBILIZATION OF CHEMICALLY-MODIFIED TRYPSIN ON DEAE-CELLULOSE

The surface charge on a protein may be changed for binding to ion-exchangers. Trypsin was modified by pyromellitic dianhydride (PMDA) to increase its surface negative charges. The trypsin derivative with 29% of the amino groups modified bound (unlike trypsin) to DEAE-cellulose. The protein could be eluted quantitatively by using 0.25 M NaCl. The pH optimum and K(m) of the enzyme do not show any drastic change on immobilization. A succinylated derivative of trypsin was also prepared, and its binding to DEAE-cellulose was compared with the derivative obtained after PMDA modification. The approach described in this work provides a method for reversible immobilization of proteins/enzymes to ion-exchangers. By using this approach it is also possible to control the strength of binding by varying the extent of chemical modification.