Adams J B
School of Biochemistry, University of New South Wales, Sydney, Australia.
Biochim Biophys Acta. 1991 Jan 29;1076(2):282-8. doi: 10.1016/0167-4838(91)90279-9.
Estrogen sulphotransferase plays a major role in controlling intracellular levels of 17 beta-estradiol in human mammary cancer cells and human endometrium. Bovine estrogen sulphotransferase c-DNA has recently been cloned; the encoded protein having a maximum Mr of 35,000 (Nash, A.R. et al. (1988) Aust. J. Biol. Sci. 41, 507-516). Enzyme of Mr 35,000 by SDS-PAGE has now been isolated and cyanogen bromide-cleaved peptides sequenced. The latter were identified in the c-DNA-predicted amino acid sequence which confirms that the active enzyme (Mr approximately 70,000) exists as a dimer of identical subunits. Sequence data on similar peptides isolated from an enzyme preparation containing a protein of Mr 74,000 as the major species on SDS-PAGE, which was previously thought to represent the enzyme, suggested that this protein was transferrin. This was confirmed by PAGE, SDS-PAGE, susceptibility to neuraminidase and reaction with bovine transferrin antibody. Isoelectric focusing experiments show that active enzyme exists in two or three polymorphic forms (pI values 5.3, 5.7 and possibly 5.9) having similar physicochemical properties of polymorphic forms of transferrin so that they overlap on ion-exchange chromatography and PAGE. The enzyme shows some homology to the amino acid sequence close to the Fe-binding site in lactoferrin and the question is raised as to the possible presence of a tightly bound metal in estrogen sulphotransferase involved in the binding of adenosine 3'-phosphate 5'-phosphosulphate.
雌激素磺基转移酶在控制人乳腺癌细胞和人子宫内膜中17β-雌二醇的细胞内水平方面起主要作用。牛雌激素磺基转移酶的cDNA最近已被克隆；编码的蛋白质最大相对分子质量为35000（纳什，A.R.等人，（1988年）《澳大利亚生物科学杂志》41卷，507 - 516页）。现已分离出相对分子质量为35000的SDS - PAGE酶，并对溴化氰裂解的肽段进行了测序。在cDNA预测的氨基酸序列中鉴定出了这些肽段，这证实了活性酶（相对分子质量约为70000）以相同亚基的二聚体形式存在。从一种酶制剂中分离出的类似肽段的序列数据表明，在SDS - PAGE上以相对分子质量为74000的蛋白质为主要成分，该蛋白质以前被认为是这种酶，结果表明该蛋白质是转铁蛋白。通过PAGE、SDS - PAGE、对神经氨酸酶的敏感性以及与牛转铁蛋白抗体的反应证实了这一点。等电聚焦实验表明，活性酶以两种或三种多态形式存在（等电点值分别为5.3、5.7，可能还有5.9），它们具有与转铁蛋白多态形式相似的物理化学性质，因此在离子交换色谱和PAGE上会重叠。该酶与乳铁蛋白中靠近铁结合位点的氨基酸序列有一些同源性，并且提出了一个问题，即雌激素磺基转移酶中是否可能存在一种紧密结合的金属，参与3'-磷酸腺苷5'-磷酸硫酸酯的结合。
