Schoenmakers C H, Pigmans I G, Kaptein E, Darras V M, Visser T J
Department of Internal Medicine III, Erasmus University Medical School, Rotterdam, The Netherlands.
FEBS Lett. 1993 Nov 29;335(1):104-8. doi: 10.1016/0014-5793(93)80449-5.
The type III iodothyronine deiodinase (ID-III) catalyzes the inner ring deiodination and, thus, the inactivation of the thyroid hormones T4 and T3. ID-III activity in rat brain, rat placenta and embryonic chicken liver is inhibited by the affinity label N-bromoacetyl-T3 (BrAcT3) with an affinity similar to that of T3. Reaction of rat brain and placenta microsomes with BrAc[125I]T3 resulted in the extensive labeling of a 32 kDa protein (p32). However, p32 was also prominently labeled in fetal rat liver microsomes which have no ID-III activity. Labeling of p32 was not influenced by 100 microM substrate analogs or inhibitors of ID-III, some of which completely inhibit ID-III activity at 1 microM. BrAc[125I]T3 labeling of embryonic chicken liver microsomes did not reveal p32 or another protein possibly related to ID-III. In contrast to previous suggestions, it is unlikely that p32 represents ID-III or a subunit thereof.
Ⅲ型碘甲状腺原氨酸脱碘酶（ID-Ⅲ）催化甲状腺激素T4和T3的内环脱碘反应，从而使其失活。大鼠脑、大鼠胎盘和胚胎鸡肝中的ID-Ⅲ活性受到亲和标记物N-溴乙酰基-T3（BrAcT3）的抑制，其亲和力与T3相似。大鼠脑和胎盘微粒体与BrAc[125I]T3反应导致一种32 kDa蛋白（p32）被大量标记。然而，在没有ID-Ⅲ活性的胎鼠肝微粒体中，p32也被显著标记。p32的标记不受100 μM底物类似物或ID-Ⅲ抑制剂的影响，其中一些抑制剂在1 μM时能完全抑制ID-Ⅲ活性。胚胎鸡肝微粒体的BrAc[125I]T3标记未显示出p32或另一种可能与ID-Ⅲ相关的蛋白。与之前的推测相反，p32不太可能代表ID-Ⅲ或其亚基。
