title: Rat liver xanthine oxidoreductase: effect of adenine on the oxidase and dehydrogenase activities.
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.
authors.affiliation: University of California, School of Veterinary Medicine, Department of Molecular Biosciences, Davis 95616, USA. khagopian@ucdavis.edu
authors.forename: Kevork
authors.initials: K
authors.lastname: Hagopian
mesh_terms: D000225:Adenine / Q000494:pharmacology*; D000818:Animals; D003956:Dialysis; D004795:Enzyme Stability; D006358:Hot Temperature; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D051381:Rats; D017208:Rats, Wistar; D014968:Xanthine Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase; D000225:Adenine