Smith T M, Kirley T L
Department of Pharmacology and Cell Biophysics, College of Medicine, University of Cincinnati, 231 Bethesda Avenue, Cincinnati, OH 45267-0575, USA.
Biochim Biophys Acta. 1998 Jul 28;1386(1):65-78. doi: 10.1016/s0167-4838(98)00063-6.
An extracellular ATPase (E-type ATPase) clone was isolated from a human brain cDNA library and sequenced. The transcript shows similarity to the previously published chicken smooth muscle and rat brain ecto-ATPase cDNAs, human CD39L1 cDNA (putative human ecto-ATPase), and mammalian CD39 (lymphoid cell activation antigen, ecto-apyrase, ATPDase, ATP-diphosphohydrolase) cDNAs. The full-length human brain cDNA encodes a 529 amino acid glycoprotein with a putative membrane spanning region near each terminus, with the majority of the protein found extracellularly. Expression of this clone in mammalian COS-1 cells yielded NaN3-sensitive ATPase and ADPase activity detectable both on intact cells and cell membrane preparations. The nucleotide hydrolysis ratio of the expressed protein is approx. 2.75:1 (ATPase:ADPase activity), classifying it as an ecto-apyrase. However, this hydrolysis ratio is intermediate between that observed for the ecto-ATPases and the CD39 ecto-apyrases (L. Plesner, Int. Rev. Cytol. 158 (1995) 141-214). Quantitative analyses of amino acid identities and similarities between this ecto-apyrase and other vertebrate E-type ATPases suggest that this human brain enzyme is nearly equally related to the ecto-ATPases and the CD39s, and phylogenetic analysis suggests that it could be an ancestral enzyme from which both ecto-ATPases and CD39 ecto-apyrases are derived.
从人脑cDNA文库中分离出一个细胞外ATP酶（E型ATP酶）克隆并进行测序。该转录本与先前发表的鸡平滑肌和大鼠脑外切ATP酶cDNA、人CD39L1 cDNA（推定的人外切ATP酶）以及哺乳动物CD39（淋巴细胞活化抗原、外切焦磷酸酶、ATP二磷酸酶、ATP - 二磷酸水解酶）cDNA具有相似性。全长人脑cDNA编码一种529个氨基酸的糖蛋白，在每个末端附近有一个推定的跨膜区域，大部分蛋白质位于细胞外。该克隆在哺乳动物COS - 1细胞中的表达产生了对NaN3敏感的ATP酶和ADP酶活性，在完整细胞和细胞膜制剂上均可检测到。所表达蛋白质的核苷酸水解比率约为2.75:1（ATP酶：ADP酶活性），将其归类为外切焦磷酸酶。然而，该水解比率介于外切ATP酶和CD39外切焦磷酸酶所观察到的比率之间（L. Plesner，《国际细胞生物学评论》158 (1995) 141 - 214）。对该外切焦磷酸酶与其他脊椎动物E型ATP酶之间氨基酸同一性和相似性的定量分析表明，这种人脑酶与外切ATP酶和CD39的关系几乎相同，系统发育分析表明它可能是外切ATP酶和CD39外切焦磷酸酶共同的祖先酶。
