title: Characterization of polyethylene glycol-modified L-asparaginase from Escherichia coli and its application to therapy of leukemia.
abstract: For the purpose of clinical application to the therapy of human leukemia and lymphosarcoma, L-asparaginase from Escherichia coli was modified with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine (activated PEG2) by an improved method, which involves a purification step of activated PEG2 by gel filtration. The PEG2-modified asparaginase retained approximately 30% (73 IU/mg of protein) of the enzymic activity of the native enzyme, while it had almost wholly lost the immunoreactivity towards anti-asparaginase antibodies. The modified enzyme retained the characteristics of the native enzyme in terms of the pH- and temperature-dependencies of activity and stability, and the Km value for L-asparagine. Administration of the modified enzyme to a dog with spontaneous lymphosarcoma induced complete remission without any toxic side effects. Seven children with multiple relapses of acute leukemia were treated with a regimen of cycles of methotrexate and native asparaginase. Three of these children developed anaphylactic shock. In contrast to the native enzyme, the successive administration of PEG2-modified asparaginase to those three patients was therapeutically effective without causing any allergic reaction.
mesh_terms: D000293:Adolescent; D000818:Animals; D001215:Asparaginase / Q000627:therapeutic use*; D002648:Child; D004285:Dogs; D004926:Escherichia coli / Q000201:enzymology*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007938:Leukemia / Q000188:drug therapy*; D008297:Male; D008970:Molecular Weight; D011092:Polyethylene Glycols / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: D011092:Polyethylene Glycols; D001215:Asparaginase