Nucleotide Pyrophosphatase of Rat Liver
Nucleotide Pyrophosphatase of Rat Liver
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大鼠肝脏核苷酸焦磷酸酶
DOI：
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发表时间：
1975
期刊：
影响因子：
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通讯作者：
K. Decker
中科院分区：
文献类型：
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作者：
E. Bischoff;T. Tran‐Thi;K. Decker
对大鼠肝核苷酸焦磷酸酶活性的亚细胞分布研究表明，它只存在于质膜和内质网中。来自这两种来源的酶都被胰酶特异性地溶解，而它们的催化性质没有明显的变化。经DEAE-纤维素柱层析、AMP亲和层析、Sephadex G-200凝胶过滤、凝胶电泳法纯化，纯化倍数分别为2000倍和1600倍。两种核苷酸焦磷酸酶均为电泳均一的可溶性蛋白。它们被证明含有碳水化合物部分。这两种酶在聚丙烯酰胺凝胶中的电泳率在三个pH值下是相同的。十二烷基硫酸盐凝胶电泳法显示两种糖蛋白的相对分子质量均为137000。
这些酶能降解多种嘌呤和嘧啶核苷酸，生成5‘-核苷一磷酸。腺苷3‘：5’-单磷酸、核酸和磷酸单酯不被切割，但对-硝基苯基-胸腺嘧啶核苷5‘-单磷酸很容易被水解。鉴于其底物和抑制物的特殊性，这些酶被认为是核苷酸焦磷酸酶而不是磷酸二酯酶。
Studies on the subcellular distribution of ratliver nucleotide pyrophosphatase activity revealed its presence in the plasma membrane and the endoplasmic reticulum only. The enzymes from either source were solubilized specifically with trypsin without an apparent change of their catalytic properties. A 2000-fold and 1600-fold purification, respectively, was achieved by a procedure including DEAE-cellulose and affinity-chromatography with AMP as ligand, gel filtration on Sephadex G-200 and gel electrophoresis. Both nucleotide pyrophosphatases were isolated as electrophoretically homogeneous soluble proteins. They were shown to contain carbohydrate moieties. The electrophoretic mobility of both enzymes in polyacrylamide gels was identical at three pH values. Dodecylsulfate gel electrophoresis indicated a molecular weight of 137000 for both glycoproteins.
The enzymes hydrolyze a variety of purine and pyrimidine nucleotides yielding a 5′-nucleoside monophosphate. Adenosine 3′:5′-monophosphate, nucleic acids and phosphate monoesters are not cleaved, but p-nitrophenyl-thymidine 5′-monophosphate is readily hydrolyzed. In view of their substrate and inhibitor specificities the enzymes are considered nucleotide pyrophosphatases rather than phosphodiesterases.