Comparative studies on the N-oxidation of aniline and N,N-dimethylaniline by rabbit liver microsomes.
1. Rate studies of N-oxidation of aniline and N,N-dimethylaniline by rabbit liver microsomal preparations were performed at different pH values. The apparent pKs of the free functional groups were 7-2 and 6-9, respectively, at 26 degrees. The apparent heats of ionization of these groups varied from 26-8 to 31-8 kJ mol-1. 2. Photo-oxidation of the microsomal mixed function oxidase resulted in rapid loss of N-oxygenating activity. The enzyme was markedly protected from inactivation by the presence of aniline or N,N-dimethylaniline. The apparent KD values for protection were close to the Km and KS values for the individual arylamines. The pH profiles of the initial rates of photo-inactivation resembled the titration curves of groups with an apparent pKa between 6-0 and 6-2. 3. The N-oxidase was strongly inhibited by diethyl pyrocarbonate at pH 6-2. 3. The N-oxidase was strongly inhibited by diethyl pyrocarbonate at pH 6-0. Catalytic capacity was partially restored by treatment with neutral hydroxylamine. Pyridine protected the enzyme from acylation. 4. A close relationship exists between the N-hydroxylation of aniline and the N-oxide formation from N,N-dimethylaniline with respect to sensitivity to photo-oxidation, reactivity to protective substrates and susceptibility to carbethoxylation.
D000814:Aniline Compounds / Q000378:metabolism*; D000818:Animals; D004047:Diethyl Pyrocarbonate / Q000378:metabolism; D005260:Female; D006863:Hydrogen-Ion Concentration; D006898:Hydroxylamines / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010084:Oxidation-Reduction; D010777:Photochemistry; D011817:Rabbits; D051381:Rats
D000814:Aniline Compounds; D006898:Hydroxylamines; D006899:Mixed Function Oxygenases; D004047:Diethyl Pyrocarbonate