Abstract:
Non-CYP oxidase enzymes are important system in biotransformation of drugs and environmental pollutants.
Molybdenum containing oxidase enzymes such as aldehyde oxidase and xanthine oxidase are constitutive tissue enzymes that metabolize several drug moieties. Herein, we evaluated the circadian rhythm of these two
enzymes in mice liver using different substrate/oxygen donor couples. Aldehyde oxidase showed typical
rhythmic fluctuation with peak activity at night cycle and minimum activity at light cycle using
pthalazine/ferricyanide and 3-methylisoquinoline/ferricyanide substrates. On the other hand, xanthine oxidase
showed interrupted diurnal rhythm, however peak and minimum enzyme activities were similar to aldehyde
oxidase circadian rhythm. In conclusion, diurnal rhythm of both molybdenum hydroxylase enzymes was
confirmed and validated in mice liver tissue that might provide further insights in the experimental evaluation of
phase-I pharmacokinetics for new drugs.
