Fekkes D, Hennemann G, Visser T J
Biochem J. 1982 Mar 1;201(3):673-6. doi: 10.1042/bj2010673.
The enzymic 5'-deiodination of 3',5'-di-iodothyronine and 5-deiodination of 3,3',5-tri-iodothyronine by rat liver microsomal fractions were found to be characterized by apparent Km values of 0.77 and 17.4 microM respectively, 3',5'-Di-iodothyronine was a competitive inhibitor of 3,3',5-tri-iodothyronine 5-deiodination (Ki 0.65 microM) and 3,3',5-tri-iodothyronine was a competitive inhibitor of 3',5'-di-iodothyronine 5'-deiodination (Ki 19.6 microM). In addition, several radiographic contrast agents and iodothyronine analogues inhibited both reactions competitively and with equal potencies (r = 0.999). These results strongly suggest the existence of a single hepatic deiodinase acting on both the tyrosyl and phenolic ring of iodothyronines.
大鼠肝脏微粒体组分对3',5'-二碘甲腺原氨酸的酶促5'-脱碘作用以及对3,3',5'-三碘甲腺原氨酸的5-脱碘作用，其表观Km值分别为0.77和17.4微摩尔。3',5'-二碘甲腺原氨酸是3,3',5'-三碘甲腺原氨酸5-脱碘作用的竞争性抑制剂（抑制常数Ki为0.65微摩尔），而3,3',5'-三碘甲腺原氨酸是3',5'-二碘甲腺原氨酸5'-脱碘作用的竞争性抑制剂（抑制常数Ki为19.6微摩尔）。此外，几种放射造影剂和碘甲腺原氨酸类似物对这两种反应均有竞争性抑制作用，且效力相同（相关系数r = 0.999）。这些结果有力地表明，存在一种单一的肝脏脱碘酶，可作用于碘甲腺原氨酸的酪氨酰环和酚环。
