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Takekawa K, Sugihara K, Kitamura S, Ohta S: Enzymatic and non-enzymatic reduction of brucine N-oxide by aldehyde oxidase and catalase. Xenobiotica. 2001 Nov;31(11):769-82.
1. Brucine N-oxide was reduced by aldehyde oxidase in rabbit liver cytosol in the presence of an electron donor, 2-hydroxypyrimidine, under anaerobic conditions. The flavoprotein purified from rabbit liver exhibited significant reductase activity in the presence of electron donors. 2. Brucine N-oxide was also reduced by rabbit liver cytosol and blood in the presence of both a reduced pyridine nucleotide and FAD under anaerobic conditions. The N-oxide reductase activities were inhibited by carbon monoxide and air. However, these activities were not abolished whe n liver cytosol and blood were boiled. Rabbit erythrocytes exhibited the reductase activity, but not plasma. 3. When liver cytosol or blood was separated by DEAE-cellulose column chromatography, the fractions with the reducing activity in the presence of both NADH and FAD also showed catalase activity. 4. Catalase catalysed the brucine N-oxide reduction in the presence of both NAD (P) H and FAD. Hematin also exhibited the reductase activity in the presence of both NAD (P) H and FAD. Photochemically reduced FAD was effective in the reduction instead of NAD (P) H and FAD. 5. Bricine N-oxide reduction proceeds via two routes in liver cytosol and blood. One is enzymatic reduction by aldehyde oxidase; the other is non-enzymatic reduction catalysed by the haem group of catalase in the presence of reduced flavin. |
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