Alvarez A, Chayet L, Galleguillos M, García L, Kettlun A M, Collados L, Traverso-Cori A, Mancilla M, Valenzuela M A
Departamento de Bioquímica y Biología Molecular, Facultad de Ciencas Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile.
Int J Biochem Cell Biol. 1996 Jan;28(1):75-9. doi: 10.1016/1357-2725(95)00114-x.
ATP-diphosphohydrolase (or apyrase) hydrolyses nucleoside di- and triphosphates in the presence of millimolar concentration of divalent cations. It is insensitive towards sulfhydryl and aliphatic hydroxyl-selective reagents and to specific inhibitors of ATPases. We present further evidence that ATPase and ADPase activities present in rat mammary gland correspond to apyrase. Two kinetic approaches have been employed, competition plot and chemical modification with group-selective reagents. The M(r) of these activities was determined by 60Co radiation-inactivation. The kinetic approaches employed, competition plot (which discriminate whether competitive reactions occur at the same site) and chemical modification, point to the presence of a single protein which hydrolyses ATP and ADP. The similar M(r) values of ATPase and ADPase activities also support this proposal. ATPase and ADPase activities of mammary gland show a similar sensitivity or insensitivity towards several chemical modifiers. These results suggest that this enzyme is ATP-diphosphohydrolase, also known as apyrase. The results obtained are compared with the ones obtained by us and other authors with the enzyme isolated from other sources.
ATP二磷酸水解酶（或腺苷三磷酸双磷酸酶）在毫摩尔浓度的二价阳离子存在下能水解核苷二磷酸和三磷酸。它对巯基和脂肪族羟基选择性试剂以及ATP酶的特异性抑制剂不敏感。我们提供了进一步的证据，表明大鼠乳腺中存在的ATP酶和ADP酶活性与腺苷三磷酸双磷酸酶相对应。采用了两种动力学方法，竞争曲线法和用基团选择性试剂进行化学修饰法。这些活性的相对分子质量通过钴60辐射失活法测定。所采用的动力学方法，竞争曲线法（用于判别竞争性反应是否发生在同一部位）和化学修饰法，都表明存在一种能水解ATP和ADP的单一蛋白质。ATP酶和ADP酶活性相似的相对分子质量值也支持这一观点。乳腺的ATP酶和ADP酶活性对几种化学修饰剂表现出相似的敏感性或不敏感性。这些结果表明这种酶是ATP二磷酸水解酶，也称为腺苷三磷酸双磷酸酶。将所得结果与我们以及其他作者从其他来源分离该酶所获得的结果进行了比较。
