Kobayashi R, Sun X Y, Walsh J H
Center for Ulcer Research and Education, University of California, Los Angeles School of Medicine.
Gastroenterology. 1991 Jan;100(1):25-32. doi: 10.1016/0016-5085(91)90578-9.
To examine the potential role of angiotensin-converting enzyme as a physiological regulator of neuropeptide activity in the alimentary tract, we purified and partially characterized this enzyme from the crude membrane fraction of rabbit gastric muscles. A single-step purification from detergent-solubilized gastric membranes by affinity chromatography, using lisinopril-Sepharose, yielded an electrophoretically homogeneous peptidase composed of 180-kilodalton polypeptide. The purified enzyme represented approximately 2% of [Leu5]enkephalin-degrading activity of the original membrane preparation, and 275-fold purification was achieved. The gastric angiotensin-converting enzyme hydrolyzed synthetic substrates specific to the lung enzyme. It hydrolyzed angiotensin I and several other bioactive peptides, by removing their carboxyl-terminal dipeptides. The activity was completely inhibited with 10(-6) mol/L captopril. The hydrolysis of enkephalin was enhanced twofold by addition of 0.3 mol/L NACl to the assay buffer. These properties were comparable with those reported for the rabbit lung enzyme. Therefore, it was concluded that rabbit gastric muscle tissue contains membrane-bound angiotensin-converting enzyme. The results suggest a role for this enzyme as a local inactivator of bioactive peptides in the stomach wall.
为了研究血管紧张素转换酶作为消化道中神经肽活性的生理调节剂的潜在作用，我们从兔胃肌的粗膜部分纯化并部分表征了这种酶。使用赖诺普利-琼脂糖通过亲和色谱法从去污剂溶解的胃膜中进行一步纯化，得到了一种由180千道尔顿多肽组成的电泳纯肽酶。纯化后的酶约占原始膜制剂中[亮氨酸5]脑啡肽降解活性的2%，实现了275倍的纯化。胃血管紧张素转换酶水解肺酶特有的合成底物。它通过去除其羧基末端二肽来水解血管紧张素I和其他几种生物活性肽。该活性被10(-6)mol/L卡托普利完全抑制。通过向测定缓冲液中加入0.3mol/L氯化钠，脑啡肽的水解增强了两倍。这些特性与报道的兔肺酶的特性相当。因此，得出结论，兔胃肌组织含有膜结合的血管紧张素转换酶。结果表明该酶作为胃壁中生物活性肽的局部失活剂发挥作用。
