Rat liver xanthine oxidoreductase: effect of adenine on the oxidase and dehydrogenase activities.

Ital J Biochem

University of California, School of Veterinary Medicine, Department of Molecular Biosciences, Davis 95616, USA.

Published: March 2007

AI Article Synopsis

  • Adenine significantly reduced xanthine oxidase (XO) and total oxidase plus dehydrogenase (XO+XDH) activities in rat liver extracts, with a decrease of 45-60% observed.
  • Dialysis removal of adenine restored XO and XO+XDH activities to near pre-dialysis levels, indicating adenine's inhibitory influence can be reversed.
  • The presence of DTT/PMSF affected enzyme stability during storage, and temperature incubation enhanced activities, but adenine’s impact persisted, suggesting it plays a role in maintaining enzyme activity under various conditions.

Article Abstract

Xanthine oxidase (XO) and total oxidase plus dehydrogenase (XO+XDH) activities from rat liver were measured in the presence or absence of adenine in extracts prepared with or without DTT/PMSF in homogenization buffer. Presence of adenine in extracts, prepared with or without DTT/PMSF, caused a 45-60% decrease in XO and XO+XDH activities. Removal of adenine by dialysis from extracts prepared with or without DTT/PMSF resulted in the recovery of XO and XO+XDH activities to almost their pre-dialysis control levels. Enzyme activity after 24hr storage at -20 degrees C depended on the presence or absence of DTT/PMSF and adenine, with both XO and XO+XDH activities being lower in extracts with the combined presence of DTT/PMSF and adenine. Incubation of extracts at 37 degrees C for 30 minutes resulted in increased XO and XO+XDH activities, however, adenine-treated samples did not differ from their pre-incubation activities. The molecular mass of the enzyme from control and adenine-treated extracts was unchanged (300 kDa). Adenine-treated extracts prepared with or without DTT/PMSF showed higher D/O ratios in all post-dialysis samples when compared with their pre-dialysis ratios. The results suggest that adenine may play a role in preventing the dehydrogenase to oxidase conversion during extract preparation, storage, overnight dialysis and heat treatment.

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