Czuba B, Vessey D A
Biochem J. 1981 Apr 1;195(1):263-6. doi: 10.1042/bj1950263.
The enzymological basis for the ability of mammalian liver to conjugate bile acids with both glycine and taurine, and for non-mammalian liver to make only taurine conjugates, was investigated. The taurine-conjugating enzyme has been purified 1200-fold from the liver of domestic fowl and its properties compared with those of the glycine/taurine-conjugating enzyme from bovine liver [Czuba & Vessey (1980) J. Biol. Chem. 255, 5296-5299]. The enzyme from both species followed a Ping Pong mechanism. The enzymes were also similar with respect to their affinity for taurine, although the enzyme from domestic fowl would not bind glycine. The affinity of both for cholyl-CoA was quite similar, too, and both enzymes were inhibited reversibly by p-mercuribenzoate. The enzymes, however, were quite different in size. The enzyme from domestic fowl had a mol.wt. of 63000-65000 by both gel filtration and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. This is approx. 15 000 mol.wt. units larger than the enzyme from bovine liver, and suggests a loss of genome over the course of evolution as the basis for the altered specificity at the amino-acid binding site.
对哺乳动物肝脏能够将胆汁酸与甘氨酸和牛磺酸进行结合，以及非哺乳动物肝脏仅生成牛磺酸结合物的酶学基础进行了研究。已从家鸡肝脏中纯化出牛磺酸结合酶，其纯化倍数达1200倍，并将其性质与来自牛肝脏的甘氨酸/牛磺酸结合酶的性质进行了比较[祖巴和维西（1980年）《生物化学杂志》255, 5296 - 5299]。这两种动物的酶均遵循乒乓机制。这两种酶对牛磺酸的亲和力也相似，尽管家鸡的酶不结合甘氨酸。它们对胆酰辅酶A的亲和力也相当相似，并且两种酶都被对汞苯甲酸可逆抑制。然而，这两种酶在大小上有很大差异。通过凝胶过滤和十二烷基硫酸钠/聚丙烯酰胺凝胶电泳测定，家鸡的酶分子量为63000 - 65000。这比牛肝脏的酶大约大15000道尔顿分子量单位，这表明在进化过程中基因组的丢失是氨基酸结合位点特异性改变的基础。
