title: Inactivation of urate oxidase by a system composed of lactoperoxidase, hydrogen peroxide and bromide.
abstract: Urate oxidase from Candida utilis, an enzyme containing an essential thiol, was examined for its sensitivity to lactoperoxidase, an oxidant present in breast milk. Upon exposure to a system composed of lactoperoxidase, hydrogen peroxide and bromide at moderately alkaline pH, the urate oxidase exhibited comparable activity to the untreated enzyme; but upon exposure at moderately acidic pH, it lost its activity completely. Thus the lactoperoxidase-H2O2-bromide system significantly inactivated urate oxidase only at moderately acidic pH. This inactivation was prevented by the presence of N-acetylmethionine, a methionine analogue, or glutathione, which is a thiol compound analogous to an amino acid, indicating that it was probably due to the oxidation and damage of the methionine residue and/or the thiol group in the urate oxidase by the lactoperoxidase system, that loss of catalytic activity of the urate oxidase occurred.
authors.affiliation: Department of Oral Biochemistry, School of Dentistry, Health Sciences University of Hokkaido, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Odajima
authors.forename: M
authors.initials: M
authors.lastname: Onishi
mesh_terms: D001965:Bromides / Q000494:pharmacology*; D002175:Candida / Q000201:enzymology; D005978:Glutathione / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007784:Lactoperoxidase / Q000494:pharmacology*; D008715:Methionine / Q000031:analogs & derivatives / Q000494:pharmacology; D017680:Potassium Compounds / Q000494:pharmacology*; D014503:Urate Oxidase / Q000037:antagonists & inhibitors*
chemical_list: D001965:Bromides; D017680:Potassium Compounds; C006379:N-acetylmethionine; D008715:Methionine; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; D014503:Urate Oxidase; D005978:Glutathione; C039004:potassium bromide