Dissociation of milk xanthine oxidase and effect of some potent inhibitors on its catalytic function

ABSTRACT

Milk xanthine oxidase [XO] was prepared and purified by gel chromatographic analysis. Chromatographic runs were made on sephadex G200 column saturated with urea. The elution profile recorded two peaks Dimeric and monomeric xanthine oxidase, respectively. The inhibitory effect of bisulfite, folate and ascorbate on the catalytic activity of xanthine oxidase was monitored by incubating the enzyme with different concentrations of these inhibitors. On assaying aliquot sample of the incubation mixture in a standardized method, a pronounced lag in rate production was recorded spectrophotometrically at 290 nm. XO activity increased from zero until substrate became limiting, but in case of inhibition the rate of catalysis never reached maximal velocity compared to control. Besides the inhibitory mechanism of morin and myricetin as flavonoids on XO activity were also studied by kinetic analysis. It was concluded that bisulfite, folate, ascorbate and flavonoids could be utilized in chemotherapy of hyperuricemia or gout