title: Oxidation of tryptophan-P-1 and P-2 by beef liver catalase-H2O2 intermediate: comparison with horseradish peroxidase.
abstract: Tryptophan-p-1 (trp-p-1) and p-2, which have high mutagenic and carcinogenic potential, are oxidized by catalase- and horseradish peroxidase (HRP)-H2O2 intermediates with optimum pH 5.9 (0.2 M-acetate) in catalase and pH 5.0 (0.2 M-acetate), 8.0 (0.01 M-phosphate) in HRP. The rate constants (k4) of the oxidation in the catalase at pH 5.9 (0.2 M-acetate) were 2965 M-1 x sec-1 for trp-p-1 and 576 M-1 x sec-1 for trp-p-2. In the case of HRP, 1894 M-1 x sec-1, (pH 5.0, 0.2 M-acetate) for trp-p-1 and 705 M-1 x sec-1 (pH 8.0, 0.001 M-phosphate) for trp-p-2 under each optimum condition. The oxidation products of trp-p-1 and p-2 by catalase or HRP lost completely their mutagenic potential in the mutation assay.
mesh_terms: D000818:Animals; D002243:Carbolines / Q000378:metabolism* / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism*; D002417:Cattle; D004353:Drug Evaluation, Preclinical / Q000379:methods; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007211:Indoles / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D009154:Mutation; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D011485:Protein Binding; D012486:Salmonella typhimurium / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002243:Carbolines; D007211:Indoles; C019133:3-amino-1-methyl-5H-pyrido(4,3-b)indole; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D010544:Peroxidases; D002374:Catalase; C019132:3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole