Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of the xenobiotic metabolizing enzymes, aldehyde oxidase and xanthine oxidase, were determined in partially purified fractions of adult guinea-pig liver at given times in the day or night. A marked circadian variation in aldehyde oxidase activity was observed with several substrates (phthalazine, phenanthridine, N-phenylquinolinium and 3,4-dihydro-4-hydroxy-3-methyl-2-quinazolinone). The main peak occurred at 0300 hr with minimum activity from 1200 to 1800 hr, the differences between rhythmic extremes being statistically significant (P less than 0.005). Xanthine oxidase activity also exhibited a daily rhythm but with a lower amplitude. Guinea-pig serum melatonin showed a synchronous circadian fluctuation with peak values at 0300 hr falling throughout the day to a minimum at 1800 hr. Exogenously administered melatonin caused a significant increase in aldehyde oxidase activity at 0900 and 1200 hr and in xanthine oxidase activity at 0900 hr. It was concluded that melatonin concentrations may be related to the circadian variation in liver molybdenum hydroxylase activity.
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PMID:Diurnal variation and melatonin induction of hepatic molybdenum hydroxylase activity in the guinea-pig. 271 20

Flavonoids are an important group of natural compounds that can interfere with the activity of some enzymes. In this study, effects of various flavonoids on aldehyde oxidase (AO) activity were evaluated in vitro. AO was partially purified from guinea pig liver. The effects of 12 flavonoids from three subclasses of flavon-3-ol, flavan-3-ol and flavanone on the oxidation of vanillin and phenanthridine as substrates of AO and xanthine as a substrate of xanthine oxidase (XO) were investigated spectrophotometrically. Among the 12 flavonoids, myricetin and quercetin were the most potent inhibitors of both AO and XO. In general, the oxidation of vanillin was more inhibited by flavonoids than that of phenanthridine. Almost all of the flavonoids inhibited AO activity more potently than XO, which was more evident with non-planner flavanols. A planner structure seems to be essential for a potent inhibitory effect and any substitution by sugar moieties reduces the inhibitory effects. This study could provide a new insight into AO natural inhibitors with potential to lead to some food-drug interactions.
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PMID:Inhibitory effects of flavonoids on aldehyde oxidase activity. 1860 46