A novel protein modification method was developed by integrating the advantages of polysialic acid (PSA) and polyethylene glycol (PEG). PSA was activated by two steps:the aldehyde group was generated by periodate oxidation at the non⁃reducing end, and then the active thiol group was formed using cystamine. The activated PSA(3�4×104) reacted with hetero⁃bifunctional PEG(3�5×103) to form a block co⁃polymer, and modified uricase at 4 ℃. The conjugate was purified with gel permeation chromatography and the target peak was collected and identified with chemical method and SDS⁃PAGE. The molecular weight of the conjugate was 5�214 × 105 through multi⁃angle laser light scattering gel system. Compared with native enzyme,residual enzyme activity was 72�4%,and heat inactivation half life in vitro was improved from 115�5 h up to 231 h. The tolerance stability from heat, acid and alkaline, trypsin treatment was significantly improved.%探索一种综合聚唾液酸（ PSA）和聚乙二醇（ PEG）优势的蛋白修饰方法。对纯化的聚唾液酸进行两步活化，先在非还原端氧化产生活性醛基，再加入胱胺形成活性巯基；活化的聚唾液酸（相对分子质量为3�4×104）和异基双功能的PEG（相对分子质量为3�5×103）形成嵌段聚合物，然后于4℃修饰尿酸酶。利用凝胶层析（Toyopearl HW 55F）对修饰后的尿酸酶进行纯化，收集相应峰进行化学法和SDS PAGE电泳鉴定，经多角度激光光散射凝胶系统测定缀合物相对分子质量为5�214×105；相对于原始酶，修饰酶酶活保留率72�4％，体外热失活半衰期由115�5 h提高到231 h，对高温、酸碱、胰蛋白酶的耐受稳定性显著提高。
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