Chemical modification of L-asparaginase from Escherichia coli with a modified polyethyleneglycol under substrate protection conditions.

L-Asparaginase was chemically modified with 2,4-bis(O-methoxypolyethyleneglycol)-6-chloro-S-triazine (mPEG2) in the presence of L-asparagine. Optimal modification was performed under the condition that the molar ratio of mPEG2/-NH2 is 10. The modified enzyme retained 33% of initial enzymatic activity with complete abolishment of immunogenicity.