人胎盘ATP二磷酸水解酶：生化特性、调节与功能 - Suppr | 超能文献

人胎盘ATP二磷酸水解酶：生化特性、调节与功能

Human placental ATP-diphosphohydrolase: biochemical characterization, regulation and function.

Kettlun A M, Alvarez A, Quintar R, Valenzuela M A, Collados L, Aranda E, Banda A, Chayet L, Chiong M, Mancilla M

Departmento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago.

Int J Biochem. 1994 Mar;26(3):437-48. doi: 10.1016/0020-711x(94)90065-5.

Abstract

Kinetic and physico-chemical studies on human placental microsomal fraction confirmed that the ATPase and ADPase activities detected in this fraction correspond to the enzyme ATP-diphosphohydrolase or apyrase (EC 3.6.1.5). These include substrate specificity, and coincident M(r) and pI values of both ATPase-ADPase activities. 2. This enzyme hydrolyses both the free unprotonated and cation-nucleotide complex, the catalytic efficiency for the latter being considerably higher. 3. Microsomal apyrase is insensitive to ouabain and Ap5A. The highly purified enzyme was only inhibited by o-vanadate, DES and slightly by DCCD. 4. Apyrase seems to be a glycoprotein from its interaction with Concanavalin-A. 5. Preliminary studies on the essential amino acid residues suggest the participation of Arg, Lys and His residues, and discard the requirement of -SH, COO-, -OH, and probably also Tyr and Trp. 6. Two kinetic modulatory proteins of apyrase were detected in placental tissue. An activating protein was found in the soluble fraction and an inhibitory protein was loosely bound to the membranes. 7. The proposed in vivo function for apyrase is related to the inhibition of platelet aggregation due to its ADPase activity, which is supported by the direct effect on washed platelets and by its plasma membrane localization.

摘要

对人胎盘微粒体部分的动力学和物理化学研究证实，该部分中检测到的ATP酶和ADP酶活性与ATP二磷酸水解酶或腺苷三磷酸双磷酸酶（EC 3.6.1.5）相对应。这些包括底物特异性，以及ATP酶 - ADP酶活性的一致相对分子质量（M(r)）和等电点（pI）值。2. 该酶可水解游离的未质子化形式和阳离子 - 核苷酸复合物，对后者的催化效率明显更高。3. 微粒体腺苷三磷酸双磷酸酶对哇巴因和Ap5A不敏感。高度纯化的该酶仅受邻钒酸盐、二乙基亚砜（DES）抑制，且受二环己基碳二亚胺（DCCD）的抑制作用较弱。4. 腺苷三磷酸双磷酸酶与伴刀豆球蛋白A相互作用，似乎是一种糖蛋白。5. 对必需氨基酸残基的初步研究表明，精氨酸（Arg）、赖氨酸（Lys）和组氨酸（His）残基参与其中，排除了对 -SH、-COO-、-OH的需求，可能还排除了对酪氨酸（Tyr）和色氨酸（Trp）的需求。6. 在胎盘组织中检测到两种腺苷三磷酸双磷酸酶的动力学调节蛋白。在可溶性部分发现一种激活蛋白，一种抑制蛋白则松散地结合在膜上。7. 腺苷三磷酸双磷酸酶在体内的假定功能与其ADP酶活性导致的血小板聚集抑制有关，这一点得到了对洗涤血小板的直接作用及其在质膜定位的支持。