title: Chemical modification of tryptophanase from E. coli with polyethylene glycol to reduce its immunoreactivity towards anti-tryptophanase antibodies.
abstract: Escherichia coli tryptophanase was modified with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine (activated PEG2, MW 5,000 x 2). The modified tryptophanase, in which approximately 43% of the total 120 amino groups and 38% of the total 16 sulfhydryl groups in the molecule were coupled, completely lost the immunoreactivity towards anti-tryptophanase serum from rabbit. Approximately 10% of the enzymic activity was retained. The modified enzyme showed the same physicochemical properties as the native enzyme: Km value for L-tryptophan (0.3 mmol/l), optimum pH (8.0) and optimum temperature (50 degrees C). The modified enzyme was more resistant than the native counterpart against proteolytic digestion with trypsin.
mesh_terms: D000818:Animals; D004926:Escherichia coli / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007106:Immune Sera / Q000276:immunology*; D007700:Kinetics; D008190:Lyases / Q000276:immunology*; D011092:Polyethylene Glycols; D011817:Rabbits; D013696:Temperature; D014357:Trypsin; D014364:Tryptophan / Q000378:metabolism; D014368:Tryptophanase / Q000276:immunology*
chemical_list: D007106:Immune Sera; D011092:Polyethylene Glycols; D014364:Tryptophan; D014357:Trypsin; D008190:Lyases; D014368:Tryptophanase