Prasad C, Peterkofsky A
J Biol Chem. 1976 Jun 10;251(11):3229-34.
Using a radioimmunoassay method for thyrotropin-releasing hormone, the presence of thyrotropin-releasing hormone-metabolizing activity in various hamster tissues was demonstrated. While there was substantial activity degrading thyrotropin-releasing hormone in hypothalamus, there was a notable absence of such activity in pituitary. The enzymatic activity in the hypothalamus was shown to be soluble and separable into two fractions. Analysis of the metabolic products formed by the two enzymes indicated that one possessed an amidase activity (less than Glu-His-Pro-NH2 leads to less than Glu-His-Pro) and the other possessed pyroglutamylpeptidase activity (less than Glu-His-Pro-NH2 leads to less than Glu+His-Pro-NH2). Other peptides containing NH2-terminal pyroglutamic acid or COOH-terminal amide groups did not block the hydrolysis of thyrotropin-releasing hormone, suggesting that the enzymes were specific. Some inhibitors preferentially blocked the activity of one or the other enzymes. Of possible biological significance is the observation that thyroid-stimulating hormone inhibited the amidase activity while hydrocortisone inhibited the pyroglutamylpeptidase activity.
采用放射免疫分析法检测促甲状腺激素释放激素，结果表明，仓鼠的各种组织中存在促甲状腺激素释放激素代谢活性。虽然下丘脑存在大量降解促甲状腺激素释放激素的活性，但垂体中明显缺乏这种活性。下丘脑的酶活性是可溶的，可分为两个部分。对这两种酶形成的代谢产物的分析表明，一种具有酰胺酶活性（Glu-His-Pro-NH2转变为Glu-His-Pro），另一种具有焦谷氨酰肽酶活性（Glu-His-Pro-NH2转变为Glu+His-Pro-NH2）。其他含有NH2末端焦谷氨酸或COOH末端酰胺基团的肽并未阻断促甲状腺激素释放激素的水解，这表明这些酶具有特异性。一些抑制剂优先阻断其中一种或另一种酶的活性。具有潜在生物学意义的是，观察到促甲状腺激素抑制酰胺酶活性，而氢化可的松抑制焦谷氨酰肽酶活性。
