Nishida M, Sato K, Kawada J
Faculty of Pharmaceutical Sciences, University of Tokushima, Shomachi, Japan.
Biochem Int. 1990 Oct;22(2):369-78.
Thyroid peroxidase (TPO), the major enzyme in the thyroid hormone synthesis, multifunctionally catalyzes (1) iodide oxidation, (2) iodination of the precursor protein, and (3) a coupling reaction of iodotyrosyl residues. The present study was carried out to examine the mercurial effects on the iodination, the second step of TPO. Purified porcine thyroglobulin or bovine serum albumin as acceptor protein was iodinated with [125I]NaI and H2O2 by purified porcine TPO. Iodinated protein was separated by acid precipitation on membrane filter or paper chromatography. Both CH3HgCl and HgCl2 dose-dependently inhibited the iodination, but HgCl2 was more potent to inhibit the iodination than CH3HgCl. These mercurial effects on the second step resemble the effects on the third step which were already reported; but are in marked contrast to the effects on the first step, where TPO was inhibited by HgCl2 but never by CH3HgCl.
甲状腺过氧化物酶（TPO）是甲状腺激素合成中的主要酶，具有多种功能，可催化（1）碘化物氧化、（2）前体蛋白碘化以及（3）碘酪氨酸残基的偶联反应。本研究旨在考察汞对TPO第二步碘化反应的影响。用纯化的猪TPO将纯化的猪甲状腺球蛋白或牛血清白蛋白作为受体蛋白与[125I]NaI和H2O2进行碘化反应。碘化蛋白通过膜滤器上的酸沉淀或纸色谱法进行分离。甲基汞氯化物（CH3HgCl）和氯化汞（HgCl2）均呈剂量依赖性抑制碘化反应，但HgCl2比CH3HgCl更有效地抑制碘化反应。这些汞对第二步反应的影响类似于已报道的对第三步反应的影响；但与对第一步反应的影响形成显著对比，在第一步反应中，HgCl2可抑制TPO，而CH3HgCl从未有此作用。
