Qian G, Zhou J, Ma J, Wang D, He B
State Key Laboratory of Functional Polymers for Adsorption and Separation, Institute of Polymer Chemistry, Nankai University, Tianjin, P.R. China.
Artif Cells Blood Substit Immobil Biotechnol. 1996 Nov;24(6):567-77. doi: 10.3109/10731199609118882.
E. coli L-asparaginase was modified with N,O-carboxymethyl 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 alpha-chymotrypsin, but lost its activity more rapidly at high temperature (> 45 degrees 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.
在正常产物L-天冬氨酸存在的情况下，用N,O-羧甲基壳聚糖对大肠杆菌L-天冬酰胺酶进行修饰，该修饰保护了酶的活性位点。修饰后的酶保留了较高的催化活性，对胰蛋白酶和α-糜蛋白酶表现出更高的稳定性，但在高温（>45℃）下比天然酶更快地失去活性。在体内进行测试时，修饰后酶的血浆半衰期（t1/2 = 40小时）比天然酶（t1/2 = 1.6小时）长33倍以上。结果表明，修饰后的L-天冬酰胺酶在肿瘤临床治疗中可能比天然酶更有用。
