Chuang N N, Newby A C, Luzio J P
Biochem J. 1984 Dec 15;224(3):689-95. doi: 10.1042/bj2240689.
Serum 5'-nucleotidase in rat and man is derived from the plasma membrane rather than the cytosol by the criteria of inhibition with [alpha beta-methylene]ADP and antisera. In individuals with cholestasis the serum enzyme is mainly present as a high-Mr form that in the presence of the zwitterionic detergent Sulphobetaine 14 has the electrophoretic characteristics of liver plasma-membrane ectoenzyme. A minor form of 5'-nucleotidase in cholestatic serum and all the enzyme in normal serum appears to be half the molecular size of the liver plasma-membrane ectoenzyme. 5'-Nucleotidase from both normal and cholestatic rat serum was found to contain a polypeptide chain of apparent Mr 70 000 by immunoblotting techniques. It is suggested that the major form of 5'-nucleotidase in cholestatic serum is an ectoenzyme dimer derived from liver plasma membrane. All of the enzyme in normal serum and some of the enzyme in cholestatic serum is present as an active monomer derived from the ectoenzyme dimer.
根据[αβ-亚甲基]ADP和抗血清的抑制标准，大鼠和人类血清中的5'-核苷酸酶来源于质膜而非胞质溶胶。在胆汁淤积患者中，血清酶主要以高分子量形式存在，在两性离子去污剂磺基甜菜碱14存在的情况下，具有肝质膜外切酶的电泳特征。胆汁淤积血清中5'-核苷酸酶的一种次要形式以及正常血清中的所有酶似乎是肝质膜外切酶分子大小的一半。通过免疫印迹技术发现，正常和胆汁淤积大鼠血清中的5'-核苷酸酶都含有一条表观分子量为70000的多肽链。有人提出，胆汁淤积血清中5'-核苷酸酶的主要形式是源自肝质膜的外切酶二聚体。正常血清中的所有酶以及胆汁淤积血清中的一些酶以源自外切酶二聚体的活性单体形式存在。
