Visser T J, van Overmeeren-Kaptein E
Biochim Biophys Acta. 1980 Aug 13;631(2):246-52. doi: 10.1016/0304-4165(80)90299-8.
A radioimmunoassay for 3'-iodothyronine has been developed. All iodothyronine analogues (except 3,3'-diiodothyronine) showed very litte (0.02% at most) cross-reactivity, and the assay was sensitive to 1 pg 3'-iodothyronine/tube. We have studied the 5'-deiodination of 3'-5'-diiodothyronine by rat liver microsomal fraction in the presence of dithiothreitol. Production of 3'-iodothyronine at 37 degrees C was found to be linear with time of incubation up to 30 min and with concentration of microsomal protein up to 100 microgram/ml. The reaction rate reached a limit on increasing 3',5'-diiodothyronine concentration to 10 microM. The effect of pH on 3'-iodothyronine production was found to depend on 3',5'-diiodothyronine concentration. Increasing 3,5'-diiodothyronine concentration from 0.1 to 10 microM resulted in a shjift of the pH optimum from 6-6.5 to 7.5. Similar effects on the 5'-deiodination of 3,3',5'-triiodothyronine were observed, supporting the hypothesis that these reactions are catalysed by a single enzyme (iodothyronine 5'-deiodinase).
已开发出一种用于检测3'-碘甲状腺原氨酸的放射免疫分析法。所有甲状腺原氨酸类似物（3,3'-二碘甲状腺原氨酸除外）的交叉反应性都非常低（最高0.02%），该分析法对每管1皮克的3'-碘甲状腺原氨酸敏感。我们研究了在二硫苏糖醇存在的情况下，大鼠肝脏微粒体部分对3',5'-二碘甲状腺原氨酸的5'-脱碘作用。发现在37摄氏度下，3'-碘甲状腺原氨酸的生成在长达30分钟的孵育时间内与孵育时间呈线性关系，在微粒体蛋白浓度高达100微克/毫升时与微粒体蛋白浓度呈线性关系。当3',5'-二碘甲状腺原氨酸浓度增加到10微摩尔时，反应速率达到极限。发现pH对3'-碘甲状腺原氨酸生成的影响取决于3',5'-二碘甲状腺原氨酸的浓度。将3,5'-二碘甲状腺原氨酸浓度从0.1微摩尔增加到10微摩尔会导致最适pH从6 - 6.5变为7.5。观察到对3,3',5'-三碘甲状腺原氨酸的5'-脱碘作用有类似影响，支持了这些反应由单一酶（甲状腺原氨酸5'-脱碘酶）催化的假说。
