与大鼠肝细胞核膜相关的NAD⁺ 糖水解酶的特性研究

Characterization of the NAD+ glycohydrolase associated with the rat liver nuclear envelope.

作者信息

Fukishima M, Okayama H, Takahashi Y, Hayaishi O

出版信息

J Biochem. 1976 Jul;80(1):167-76. doi: 10.1093/oxfordjournals.jbchem.a131248.

DOI:10.1093/oxfordjournals.jbchem.a131248

Abstract

The localization of NAD+ glycohydrolase [EC 3.2.2.5] (NADase) in purified rat liver nuclei has been examined. Subnuclear fractionation revealed that at least 70% of the NADase in nuclei was associated with the nuclear envelope fraction. The nuclear envelope fraction was practically free of microsomal contamination as judged by electron microscopic morphometry and assays of microsomal marker enzymes. Therefore, NADase was found to be an integral component of the nuclear envelope. The enzymological properties of the nuclear envelope NADase were compared with those of the microsomal enzyme. The nuclear envelope NADase was identical to the microsomal enzyme in its Km for NAD+ (60 muM), pH optimum (pH 6.5), ratio of transglycosidase activity to NADase activity (about 0.5), thermal stability and sensitivity to various inhibitors. Thus, NADase is a common enzymic component of both the nuclear envelope and the endoplasmic reticulum.

摘要

已对纯化的大鼠肝细胞核中烟酰胺腺嘌呤二核苷酸糖水解酶EC 3.2.2.5的定位进行了研究。亚核分级分离显示，细胞核中至少70%的NAD酶与核膜部分相关。通过电子显微镜形态测定和微粒体标记酶分析判断，核膜部分几乎没有微粒体污染。因此，发现NAD酶是核膜的一个组成成分。将核膜NAD酶的酶学性质与微粒体酶的酶学性质进行了比较。核膜NAD酶在其对NAD+的米氏常数(60μM)、最适pH(pH 6.5)、转糖苷酶活性与NAD酶活性之比(约0.5)、热稳定性以及对各种抑制剂的敏感性方面与微粒体酶相同。因此，NAD酶是核膜和内质网的一种共同酶成分。