Rousset B, Poncet C, Dumont J E, Mornex R
Biochem J. 1980 Dec 15;192(3):801-12. doi: 10.1042/bj1920801.
Iodination and hormone synthesis has been studied in isolated hog thyroid cells in suspension. We characterized three iodination processes by use of pharmacological agents. (1) Intracellular iodination dependent on active iodide transport, which was inhibited by NaClO4 or ouabain, but not by catalase. This iodination was linear for 6h with no apparent Km for iodide of 1.5 muM, was stimulated by thyrotropin or N6O2'-dibutyryladenosine 3':5'-cyclic monophosphate, yielded mostly iodinated thyroglobulin and was efficient for tetraiodothyronine synthesis. (2) Extracellular iodination, which was sensitive to catalase, but not to NaClO4 or ouabain. This iodination plateaued after 2h and the apparent Km was 16.5 muM. This process was insensitive to thyrotropin and dibutyryl cyclic AMP. The major products were iodoprotein other then thyroglobulin and iodolipid and the yield of tetraiodothyronine was low. (3) Intracellular iodination from passively diffused iodide, which was not sensitive to inhibitors. Other characteristics of passive intracellular iodination were intermediate between active intracellular iodination and extracellular iodination. The fact that the three processes are inhibited by similar concentrations of methimazole, and their apparent Km values, when corrected for the concentrating effect of iodide trapping, are all of the same order as the Km of purified thyroid peroxidases, suggest that although their locations are different, the enzymic systems involved are identical. These results show that, besides an extracellular site of iodination, dispersed thyroid cells process an intracellular site of iodination with biochemical characteristics of physiological relevance.
已对悬浮状态下分离的猪甲状腺细胞中的碘化作用和激素合成进行了研究。我们通过使用药理试剂对三种碘化过程进行了表征。（1）依赖于活性碘转运的细胞内碘化作用，其受到高氯酸钠或哇巴因的抑制，但不受过氧化氢酶的抑制。这种碘化作用在6小时内呈线性，碘的表观Km值为1.5 μM，受促甲状腺激素或N6O2'-二丁酰腺苷3':5'-环磷酸腺苷刺激，主要产生碘化甲状腺球蛋白，对四碘甲状腺原氨酸的合成效率较高。（2）细胞外碘化作用，其对过氧化氢酶敏感，但对高氯酸钠或哇巴因不敏感。这种碘化作用在2小时后达到平稳状态，表观Km值为16.5 μM。该过程对促甲状腺激素和二丁酰环磷酸腺苷不敏感。主要产物是除甲状腺球蛋白外的碘蛋白和碘脂质，四碘甲状腺原氨酸的产量较低。（3）由被动扩散的碘进行的细胞内碘化作用，其对抑制剂不敏感。被动细胞内碘化作用的其他特征介于活性细胞内碘化作用和细胞外碘化作用之间。这三种过程都受到相似浓度甲巯咪唑的抑制，并且当校正碘捕获的浓缩效应时，它们的表观Km值都与纯化的甲状腺过氧化物酶的Km值处于同一数量级，这表明尽管它们的位置不同，但所涉及的酶系统是相同的。这些结果表明，除了细胞外碘化位点外，分散的甲状腺细胞还具有具有生理相关性生化特征的细胞内碘化位点。
