Enzymatic Reduction of 4-Hydroxyaminoquinoline 1-oxide to 4-Aminoquinoline 1-oxide in Mouse Liver and Lung

Objective The 4-hydroxyaminoquinoline 1-oxide reductase assay was optimized and validated using microsomal and mitochondrial fractions from mouse liver and microsomal fraction from mouse lung as the enzyme source. Methods Mouse liver and lung were weighted and minced,and subsequently were homogenized.Fractions of microsomes and mitochondria were isolated by centrifugation.In incudations of 4-hydroxyaminoquinoline 1-oxide with the enzyme source in anaerobic environment,the reduced product:4AQO was extracted and detected by spectrophotometric analysis.The production of 4-aminoquinoline 1-oxide was shown to be linear with incubation time for 30 minutes.Also,the production of 4-aminoquinoline 1-oxide was proportional to the amounts of microsomal and mitochodrial fractions in the incubations.The specific activity of 4-hydroxyaminoquinoline 1-oxide reductase was found to be nearly equal between microsomes and mitochondria of mouse liver. Results The spectific activity in liver microsomes was 2.3 times than in the lung microsomes.Activity observed in the presence of NADH was somewhat lower than with NADPH.Reduction of 4-hydroxyaminoquinoline 1-oxide was found to be stimulated by flavin coenzymes. Conclusion The 4-hydroxyaminoquinoline 1-oxide reductase mainly exists in microsomal and mitochondrial fractions of mouse liver.