Asparaginase with site-specific PEGylation as well as preparation method and application thereof

The invention discloses a PEGylated asparaginase and an application thereof. PEG is coupled to amino on N-terminal of one or two subunits of L-asparaginase, and the molecular weight of PEG is 30-40KDa. PEG is preferentially selected from branching type PEG whose activating groups are aldehyde groups. Compared with commercially available PEGylated asparaginase products, the PEGylated asparaginase has the advantages of longer half life, lower immunogenicity, homogeneous components, and higher specific activity. The product with two subunits modified by PEG whose molecular weight is 40KDa has higher activity and longer half life. The conjugate is more suitable for preparation of antitumor drugs and application to clinic treatment.