Effects of adenine on the stability and expression of xanthine dehydrogenase from Drosophila melanogaster

The in vivo effect of adenine on xanthine dehydrogenase from Drosophila melanogaster has been studied by feeding adult flies for 48 hr on regular undefined media buffered with phosphate and containing 15 mM adenine. Extracts of adenine-fed flies show 25-30% reduction in xanthine dehydrogenase activity, and 35-40% reduction in uric acid production. The adenine exposed enzyme, however, is now more stable during overnight dialysis with the loss of activity never more than 30%, while controls show losses of over 50%. Thermal stability studies reveal that the enzyme from adenine-fed flies, in contrast to that from controls, is resistant to high temperature (50°C). During the 48-hr period of feeding, enzyme activity decreases in the control flies whereas this ageing effect is less pronounced in the adenine-fed flies. Column chromatography and gel electrophoresis, using [8-¹⁴C]adenine show that adenine appears to bind to xanthine dehydrogenase, with the radioactivity peaks always corresponding with enzyme activity peaks.