Dunn A D
Endocrinology. 1984 Feb;114(2):375-82. doi: 10.1210/endo-114-2-375.
Rabbit thyroids contain cathepsin D (CD) and several thiol endopeptidases including cathepsin B and three newly described enzymes (cathepsins 180K, 110K, and 45K). The present paper assesses the relative physiological importance of these enzymes in thyroglobulin degradation in rabbits. Thyroidal thiol endopeptidase [thiol thyroglobulin hydrolase (thiol TgH)] activity increased in the absence of changes in CD activity in animals treated with 10 U bovine TSH. Peak enzyme activity occurred 24 h after injection of hormone. After 20 U bovine TSH, thiol endopeptidase activity increased by approximately 100%, whereas CD increased by 50%. The increase in thiol enzyme activity was attributed both to cathepsin B and to the other thiol endopeptidases. The lysosomal acid hydrolases acid phosphatase and dipeptidyl peptidase II were unaffected by TSH at either dose level. Thiol TgH activity, but not CD activity, was decreased in thyroids of rabbits treated with T4 [5 micrograms/(100 g BW X day)] for 1 week. All thyroidal acid hydrolases examined were suppressed in animals receiving T4 for 3 weeks. Thiol TgH activity was localized primarily to a lysosome-enriched fraction of thyroid homogenates. Our results suggest that the thiol proteases probably are the most important endopeptidases in thyroglobulin hydrolysis in vivo and that their activities are influenced by TSH.
兔甲状腺含有组织蛋白酶D（CD）和几种巯基内肽酶，包括组织蛋白酶B以及三种新描述的酶（组织蛋白酶180K、110K和45K）。本文评估了这些酶在兔甲状腺球蛋白降解中的相对生理重要性。在用10 U牛促甲状腺激素（TSH）处理的动物中，甲状腺巯基内肽酶[巯基甲状腺球蛋白水解酶（巯基TgH）]活性增加，而CD活性无变化。酶活性峰值在注射激素后24小时出现。给予20 U牛TSH后，巯基内肽酶活性增加约100%，而CD增加50%。巯基酶活性的增加归因于组织蛋白酶B和其他巯基内肽酶。溶酶体酸性水解酶酸性磷酸酶和二肽基肽酶II在两种剂量水平下均不受TSH影响。用T4[5微克/（100克体重×天）]处理1周的兔甲状腺中，巯基TgH活性降低，但CD活性未降低。接受T4处理3周的动物中，所有检测的甲状腺酸性水解酶均受到抑制。巯基TgH活性主要定位于甲状腺匀浆富含溶酶体的部分。我们的结果表明，巯基蛋白酶可能是体内甲状腺球蛋白水解中最重要的内肽酶，并且它们的活性受TSH影响。
