The salivary apyrase of the blood-sucking sand fly Phlebotomus papatasi belongs to the novel Cimex family of apyrases

Apyrases are enzymes that hydrolyze nucleotide di- and triphosphates to ort hophosphate and mononucleotides, At least two families of enzymes, belongin g to the 5'-nucleotidase and to the actin/heat shock 70/sugar kinase superf amily, have evolved independently to serve the apyrase reaction. Both famil ies require either Ca2+ or Mg2+ for their action. A novel apyrase enzyme se quence, with no homology to any other known protein sequence, was found rec ently in the salivary glands of the hematophagous bed bug Cimex lectularius . This enzyme functions exclusively with Ca2+. Here, we report the finding of a cDNA similar to that of the C. lectularius salivary apyrase isolated f rom a salivary gland cDNA library of Phlebotomus papatasi, Transfection of insect cells with the P. papatasi salivary gland apyrase cDNA resulted in t he secretion of a Ca2+-dependent apyrase whose activity was indistinguishab le from that in salivary homogenates of P. papatasi. Homologous sequences w ere found in humans, in another sand fly (Lutzomyia longipalpis), in the fr uit fly Drosophila melanogaster, in the nematode Caenorhabditis elegans and in the protozoan Cryptosporidium parvum, indicating that this family of en zymes is widespread among animal species.