Purine salvage pathways in the Australian termite, Nasutitermes walkeri hill

Abstract

Extracts of the degutted body of the termite Nasutitermes walkeri contained adenine phosphoribosyltransferase (APRT) (0.277 ± 0.014 nmol/min/mg protein) but neither hypoxanthine-guanine phosphoribosyltransferase (HGPRT) nor inosine kinase indicating that the synthesis of inosine is the committed step in the catabolism of IMP and AMP to urate. The presence of a low activity of adenosine kinase (0.025 ± 0.002 nmol/min/mg protein) may be required to prevent depletion of the adenylate pool. Bacterial extracts from the gut by contrast contained the full range of salvage enzymes including HGPRT (0.117 ± 0.003 nmol/min/mg protein), APRT (0.371 ± 0.015 nmol/min/mg protein), adenosine kinase (0.068 ± 0.025 nmol/min/mg protein) and inosine kinase (0.032 ± 0.002 nmol/min/mg protein). The inability of N. walkeri to salvage inosine and hypoxanthine suggests a mechanism for the apparently uncontrolled synthesis of urate, by termites, during laboratory storage.