Localisation and functional studies on the 5 '-nucleotidase of the cattle tick Boophilus microplus

The ecto-5'-nucleotidase from the cattle tick Boophilus microplus is an unu sual enzyme, hydrolysing a variety of nucleoside mono-, di- and triphosphat es to release the free nucleoside. The gene has been sequenced and the reco mbinant protein expressed as a functional, active enzyme. Nevertheless, the function of the enzyme in the tick remains obscure. The enzyme is present throughout the life cycle, but in largest amounts in unfed larvae and adult ticks. The tissue location has been studied in adult female ticks by Weste rn blotting, RT-PCR and immunofluorescence. All methods show the enzyme to be principally in the Malpighian tubules, though significant amounts are al so present on the surface of ovaries and in detectible amounts in other tis sues. This, together with the known specificity of the enzyme, suggests a r ole in purine salvage pathways. Sensitivity of ticks to allopurinol, an inh ibitor of hypoxanthine-guanine-phosphoribosyltransferase, supports the impo rtance of purine salvage in this tick and the potential role of nucleotidas e in this pathway.