SPACER EFFECTS ON ENZYMATIC-ACTIVITY OF PAPAIN IMMOBILIZED ONTO POROUS CHITOSAN BEADS

Papain was covalently immobilized onto the surface of porous chitosan beads without or with spacers of different lengths. The relative activ ity of the immobilized papain was found to be high toward a small eate r substrate, N-benzyl-L-arginine ethyl ester (BAEE), but rather low to ward casein, a high molecular weight substrate. Papain immobilized wit h spacer gave an almost constant activity, in marked contrast with the immobilized papain without spacer, whose activity monotonously decrea sed with decreasing surface concentration. The relative activity of th e immobilized papain for hydrolysis of a high molecular weight substra te greatly depended on the length of the spacer. The pH, thermal and s torage stabilities of the immobilized papain were higher than those of the free one, and the papain immobilized directly to the chitosan bea ds' surface without any spacer gave a higher stability than those immo bilized with spacer. The spacer's effect on the activity could be expl ained in terms of mobility of the immobilized papain molecule.