Sakakibara Y, Suiko M, Nakajima H, Liu M C
Department of Biochemistry, University of Texas Health Center at Tyler 75710.
Biochem J. 1995 Feb 1;305 ( Pt 3)(Pt 3):993-8. doi: 10.1042/bj3050993.
Chang liver cells, Caco-2 human intestinal epithelial cells and Madin-Darby canine kidney (MDCK) cells, labelled with [35S]sulphate in the presence of different concentrations of cycloheximide, produced 87.7-95.3%, 35.8-41.1% and 23.2-25.9%, respectively, of the amounts of free tyrosine O-[35S]-sulphate (Tyr[35S]) formed by corresponding cells labelled in the absence of cycloheximide. Homogenates prepared from the three kinds of cells showed the presence of enzymic activities catalysing the sulphation of L-tyrosine, with specific activities in the order: Caco-2 cells > MDCK cells > Chang liver cells. In all three cases, most of the tyrosine sulphotransferase' activity was found in the cytosolic fraction, indicating the enzyme to be a cysolic protein. A tyrosine-dependence experiment revealed that, for all three kinds of cells labelled with [35S]sulphate, the production of free Tyr[35S] was proportional to the concentration of L-tyrosine present in the culture medium. These results imply an involvement of sulphation in removing excess intracellular L-tyrosine.
在不同浓度环己酰亚胺存在的情况下，用[35S]硫酸盐标记的张氏肝细胞、Caco-2人肠上皮细胞和麦氏犬肾（MDCK）细胞，分别产生了在无环己酰亚胺情况下标记的相应细胞所形成的游离酪氨酸O-[35S]硫酸盐（Tyr[35S]）量的87.7 - 95.3%、35.8 - 41.1%和23.2 - 25.9%。由这三种细胞制备的匀浆显示存在催化L-酪氨酸硫酸化的酶活性，比活性顺序为：Caco-2细胞＞MDCK细胞＞张氏肝细胞。在所有三种情况下，大部分酪氨酸磺基转移酶活性存在于胞质部分，表明该酶是一种胞质蛋白。酪氨酸依赖性实验表明，对于所有用[35S]硫酸盐标记的三种细胞，游离Tyr[35S]的产生与培养基中L-酪氨酸的浓度成正比。这些结果表明硫酸化参与了去除细胞内过量的L-酪氨酸。
