Burbach J P, De Bree F M, Terwel D, Tan A, Maskova H P, Van der Kleij A A
Rudolf Magnus Institute, Department of Pharmacology, Utrecht University, The Netherlands.
Peptides. 1993 Jul-Aug;14(4):807-13. doi: 10.1016/0196-9781(93)90118-z.
Previously it has been shown that vasopressin (VP) and oxytocin are converted by aminopeptidase activity in brain membranes into fragments with potent CNS activities. This report concerns the properties of this enzyme activity, addressed as VP-converting aminopeptidase (VP-AP) activity, in membranes of the rat brain. The VP-AP activity had a pH optimum at pH 7.0 and had a Km of 17 microM for its action on VP. Amastatin was the most potent aminopeptidase inhibitor. Enzyme activity was inhibited by relatively low concentrations of metal chelators. Treatment of brain membranes by EDTA resulted in loss of enzyme activity that was completely reversed by 10 microM Zn2+, indicating that VP-AP activity is a metallopeptidase. Several VP analogues and fragments, in particular VP(1-8), inhibited the action of enzyme activity on VP. Among peptides unrelated to VP, angiotension I, somatostatin, and porcine ACTH(1-39) markedly inhibited enzyme activity. Solubilization of VP-AP activity from brain membranes and gel filtration on Sephadex G200 showed two peaks of activity, one eluting with an apparent mass of about 140 kDa, the other in the void volume. Gel filtration fractions were able to convert [3H][Phe3]VP in a step-wise fashion. The VP-AP-like activity was found in many tissues outside the brain. Highest activity was present in lung, kidney, parts of the gastrointestinal tract, ovary, and uterus. The results indicate that VP-AP activity is a widely distributed enzyme with probably multiple functions, one of which involves the metabolism of vasopressin in the brain.
此前已有研究表明，血管加压素（VP）和催产素在脑膜中可通过氨肽酶活性转化为具有强大中枢神经系统活性的片段。本报告关注的是大鼠脑膜中这种酶活性（称为VP转化氨肽酶（VP - AP）活性）的特性。VP - AP活性在pH 7.0时具有最佳pH值，其对VP作用的Km值为17微摩尔。抑氨肽酶素是最有效的氨肽酶抑制剂。相对低浓度的金属螯合剂可抑制酶活性。用乙二胺四乙酸（EDTA）处理脑膜会导致酶活性丧失，而10微摩尔的Zn2 +可使其完全恢复，这表明VP - AP活性是一种金属肽酶。几种VP类似物和片段，特别是VP(1 - 8)，可抑制酶活性对VP的作用。在与VP无关的肽中，血管紧张素I、生长抑素和猪促肾上腺皮质激素(1 - 39)可显著抑制酶活性。从脑膜中溶解VP - AP活性并在葡聚糖G200上进行凝胶过滤显示有两个活性峰，一个以约140 kDa的表观质量洗脱，另一个在空体积处。凝胶过滤级分能够逐步转化[3H][苯丙氨酸3]VP。在脑外的许多组织中都发现了VP - AP样活性。肺、肾、部分胃肠道、卵巢和子宫中的活性最高。结果表明，VP - AP活性是一种广泛分布的酶，可能具有多种功能，其中之一涉及脑中血管加压素的代谢。
