Site-directed pegylation of arginases and use thereof as anti-cancer and anti-viral agents

Abstract

Mono-pegylated arginase conjugate and method producing thereof. The mono-pegylated arginase is homogeneous in molecular weight and shows therapeutic effect for treating cancers and viral infections. The method of producing such arginase conjugate has a main step of genetically modifying the gene encoding an arginase so that the PEG moiety can attach to the enzyme at a predetermined, specific intended site. This is achieved by removing the PEG attaching amino acid residues at undesirable sites while keeping (or adding, if necessary) the one at the desirable site of the enzyme. Two exemplary mono-pegylated arginase conjugates so produced are human arginase I (HAI) where a polyethylene glycol (PEG) moiety is site-specific covalently bonded to Cys45 of the enzyme and Bacillus caldovelox arginase (BCA) where a polyethylene glycol (PEG) moiety is site-specific covalently bonded to Cys161 of the enzyme. 单聚乙二醇化精氨酸酶偶联物及其制备方法。所述单聚乙二醇化精氨酸酶在分子量上是均一的，并且显示出用于治疗癌症和病毒感染的治疗效果。制备所述精氨酸酶偶联物的方法包括遗传修饰编码精氨酸酶的基因使得PEG部分能够在预定的特定目标位点结合到该酶上的主要步骤。这通过除去位于该酶的不期望的位点的PEG结合氨基酸残基同时在该酶的期望的位点保留(或增加，如果需要的话)PEG结合氨基酸残基来实现。如此制备的两种示例性的单聚乙二醇化精氨酸酶偶联物是人类精氨酸酶I(HAI)和热溶芽孢杆菌精氨酸酶(BCA)，在所述人类精氨酸酶I中，聚乙二醇(PEG)部分定点共价结合到该酶的Cys45；在所述热溶芽孢杆菌精氨酸酶中，聚乙二醇(PEG)部分定点共价结合到该酶的Cys161。