Human guanine deaminase: cloning, expression and characterisation.

Abstract

Guanine deaminase activity may contribute significantly to overall urate production in mammals. In xanthine dehydrogenase deficiency, the mean urine excretion ratio for xanthine: hypoxanthine is approximately 4:11, suggesting that the conversion of guanine to xanthine may be quantitatively more important than that of hypoxanthine to xanthine, albeit the potential recycling of hypoxanthine to IMP would be expected to reduce the hypoxanthine level. In another study the relative amount of xanthine formation via guanine was estimated to be approximately 5-fold greater than via hypoxanthine2. In a porcine model, lead induced inactivation of guanine deaminase activity, resulted in the deposition of guanine crystals in the epiphyseal plate of the femoral head3. A full term infant who presented with acute anoxia and died from respiratory distress at day 2 was reported to be deficient in brain guanine deaminase activity4 .