Enzyme Design by Chemical Modification of Papain Lysine
Papain (EC 3.4.22.2) has been chemically modified using two reagents including different anhydrides of maleic and poly-maleic acids. The average ratio of modified-NH2 was tested by trinitrobenzenesulfonic acid (TNBS) method. The native and modified papain were purified by dialysis and their structures were characterized by FTIR. The factor related with the activity of the modified papain, such as temperature, pH value and kinetic constant were studied and compared with the native papain. The resultant papain had its optimum pH shifted from 6.0 to 9.0. Compared with native papain, the thermal stability and the resistance to alkali of modified enzyme were improved considerably. Among the enzyme, poly-maleic anhydride modified enzyme was found to be the best in catalytic efficiency. Keywords-chemical modification; papain; maleic anhydride;