THE CHEMICAL MODIFICATION OF E. coli L-ASPARAGINASE BY N,O-CARBOXYMETHYL CHITOSAN

E. coli L-asparaginase was modified with N, O-carboxymehtyl chitosan in the presence of normal product L-aspartic acid, which protected the active site of the enzyme. The modified enzyme remained high catalytic activity, showed greater stability against trypsin and α-chymotrypsin, but lost its activity more rapidly at high temperature (>45 °C) than did the native enzyme. When tested in vivo, the plasma half-life of the modified enzyme (t1/2 = 40 hr) was over 33 times longer than that of the native enzyme (t1/2 = 1.6 hr). The results showed that the modified L-asparaginase may be much more useful than did the native enzyme for clinical treatments of tumors.