The oxidation of 2-aminofluorene by prostaglandin endoperoxide synthetase. Comparison with other peroxidases.
We have examined the prostaglandin endoperoxide synthetase-dependent metabolism of the arylamine carcinogen 2-aminofluorene (2-AF). Ram seminal vesicle microsomes fortified with arachidonic acid metabolize 2-AF to products covalently bound to microsomal macromolecules, water-soluble metabolites, and two organic extractable metabolites. The organic extractable metabolites were identified by co-chromatography, uv-visible spectrophotometry, and mass spectrometry as 2-nitrofluorene and 2,2'-azobisfluorene (azofluorene). Hydrogen peroxide also supports 2-AF metabolism to the same products, suggesting that the hydroperoxidase activity of prostaglandin endoperoxide synthetase is responsible for the co-oxidation. The highly reactive oxygenated metabolites of 2-AF, N-hydroxy-2-AF, and 2-nitrosofluorene, are metabolized by prostaglandin endoperoxide synthetase to one major product, 2-nitrofluorene. The metabolism of 2-AF, N-hydroxy-2-AF, and 2-nitrosofluorene is extremely rapid, reaching completion in less than 30 s. The horseradish peroxidase/H2O2 system also metabolites 2-AF to 2-nitrofluorene and azofluorene. The chloroperoxidase/H2O2 system, however, yields primarily 2-nitrosofluorene from 2-AF. These results suggest that 2-AF is oxidized to an electrophilic intermediate(s) by prostaglandin endoperoxide synthetase, which either binds covalently to tissue macromolecules or is further rapidly oxidized to 2-nitrofluorene and azofluorene. Furthermore, this reaction probably proceeds through a free radical mechanism similar to that of horseradish peroxidase.
D000818:Animals; D002711:Chloride Peroxidase / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005449:Fluorenes / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D009153:Mutagens / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D012669:Seminal Vesicles / Q000201:enzymology*; D012756:Sheep
D005449:Fluorenes; D009153:Mutagens; C012177:2-aminofluorene; D006735:Horseradish Peroxidase; D010544:Peroxidases; D002711:Chloride Peroxidase; D011451:Prostaglandin-Endoperoxide Synthases