Thyroxine 5'-monodeiodination in rat anterior pituitary homogenates.
Thyroxine 5'-monodeiodination in rat anterior pituitary homogenates.
复制标题
大鼠垂体前叶匀浆中的甲状腺素 5-单碘化。
作者：
M. Kaplan
本文研究了5‘-脱碘在垂体前叶匀浆中将T4转化为T3的作用。除非加入二硫苏糖醇(DTT)或还原型谷胱甘肽，否则未见T4 5‘-单脱碘。DTT(5 Mm)引起可测量的转化率，最大转化率出现在50-100 mm DTT之间。谷胱甘肽是一种效力较小的刺激剂。T4-5‘-单脱碘依赖于pH，最大pH为7.5，温度依赖于4-37℃，预热至75℃30分钟可破坏95%以上的活性。反应速度与匀浆中的组织含量成正比。当DTT浓度低于最大值但不饱和时，氮气孵育使反应速率提高到空气下孵育的161%。5 mM EDTA、5‘Mα-生育酚、100 mM氯化钾、100-M NaL、140μ-TRH、300μ丙基硫氧嘧啶、300 HM他巴唑均无明显作用。过氧化氢酶(2000U/ml)的抑制作用随DTT浓度的不同而不同。T4 5‘-一脱碘。
The conversion of T4 to T3 by 5′-monodeiodination was studied in anterior pituitary homogenates. No T4 5′- monodeiodination was seen unless dithiothreitol (DTT) or reduced glutathione was added. DTT (5 mM) caused measurable conversion, and maximum rates occurred between 50–100 mM DTT. Glutathione was a less potent stimulant. T4 5′-monodeiodination was pH dependent, with a pH maximum of 7.5, and temperature dependent between 4–37 C. Preheating the homogenate to 75 C for 30 min destroyed more than 95% of the activity. The reaction rate was proportional to the tissue content in the homogenate. At submaximal but not at saturating DTT concentrations, incubations under nitrogen increased the reaction rate to 161% of the rates in incubations under air. There was no significant effect of 5 mM EDTA, 5′ M α-tocopherol, 100 mM KC1, 100 –M Nal, 140 μM TRH, 300 μM propylthiouracil, or 300 HM methimazole. Catalase (2000 U/ml) had a variable inhibitory effect depending on the DTT concentration. The T4 5′-monodeiodinatio...