Valenzuela J G, Belkaid Y, Rowton E, Ribeiro J M
Section of Medical Entomology, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Building 4, Room 126, MSC 0425, Bethesda, MD 20892-0425, USA.
J Exp Biol. 2001 Jan;204(Pt 2):229-37. doi: 10.1242/jeb.204.2.229.
Apyrases are enzymes that hydrolyze nucleotide di- and triphosphates to orthophosphate and mononucleotides. At least two families of enzymes, belonging to the 5'-nucleotidase and to the actin/heat shock 70/sugar kinase superfamily, have evolved independently to serve the apyrase reaction. Both families require either Ca(2+) or Mg(2+) for their action. A novel apyrase enzyme sequence, with no homology to any other known protein sequence, was found recently in the salivary glands of the hematophagous bed bug Cimex lectularius. This enzyme functions exclusively with Ca(2+). Here, we report the finding of a cDNA similar to that of the C. lectularius salivary apyrase isolated from a salivary gland cDNA library of Phlebotomus papatasi. Transfection of insect cells with the P. papatasi salivary gland apyrase cDNA resulted in the secretion of a Ca(2+)-dependent apyrase whose activity was indistinguishable from that in salivary homogenates of P. papatasi. Homologous sequences were found in humans, in another sand fly (Lutzomyia longipalpis), in the fruit fly Drosophila melanogaster, in the nematode Caenorhabditis elegans and in the protozoan Cryptosporidium parvum, indicating that this family of enzymes is widespread among animal species.
腺苷三磷酸双磷酸酶是一类能将核苷二磷酸和三磷酸水解为正磷酸盐和单核苷酸的酶。至少有两个酶家族，分别属于5'-核苷酸酶家族以及肌动蛋白/热休克70/糖激酶超家族，它们独立进化以发挥腺苷三磷酸双磷酸酶的反应功能。这两个家族的酶发挥作用均需要Ca(2+)或Mg(2+)。最近，在吸血臭虫温带臭虫的唾液腺中发现了一种与其他已知蛋白质序列无同源性的新型腺苷三磷酸双磷酸酶序列。这种酶仅在Ca(2+)存在时发挥作用。在此，我们报告从巴氏白蛉唾液腺cDNA文库中分离出与温带臭虫唾液腺苷三磷酸双磷酸酶cDNA相似的序列。用巴氏白蛉唾液腺腺苷三磷酸双磷酸酶cDNA转染昆虫细胞，导致分泌出一种依赖Ca(2+)的腺苷三磷酸双磷酸酶，其活性与巴氏白蛉唾液匀浆中的活性无法区分。在人类、另一种白蛉（长须白蛉）、果蝇、线虫秀丽隐杆线虫以及原生动物微小隐孢子虫中均发现了同源序列，这表明该酶家族在动物物种中广泛存在。
