Stewart T A, Weare J A, Erdös E G
Peptides. 1981 Summer;2(2):145-52. doi: 10.1016/s0196-9781(81)80027-7.
We purified peptidyl-dipeptidase (converting enzyme, EC 3.4.15.1) to homogeneity from the membrane fraction of human lung and for comparison, from human and hog kidney. The membrane-bound lung enzyme was purified 1800-fold with 19% yield, and the kidney enzyme 640-fold with 10% yield. The specific activities with Bz-Gly-His-Leu were 81 mumol/min/mg for the lung and 65 for the kidney enzyme. The lung enzyme was homogeneous in gel electrophoresis with Mr = 155,000 and Sw,20 = 8.0 in ultracentrifugation. Antibodies elicited against lung or kidney enzyme cross-reacted with enzyme from other organ, but not with the hog enzyme. In isoelectric focusing both human enzymes had a major form with a pI of 5.2. The lung preparation also contained more acidic forms (pI = 4--5), which were eliminated by treatment with neuraminidase. Lung and kidney converting enzyme hydrolyzed bradykinin, angiotensin I, and enkephalins and had similar kinetic constants. Bradykinin was the best substrate, as indicated by its kcat/Km, but Met5-enkephalin had the highest turnover number. The hydrolysis of Bz-Gly-His-Leu was inhibited by captopril (SQ 14225) competitively, and by Keto-ACE, a non-peptide derivative of Bz-Phe-Gly-Pro, non-competitively.
我们从人肺膜部分纯化肽基二肽酶（转化酶，EC 3.4.15.1）至同质，作为比较，还从人和猪肾中进行了纯化。膜结合的肺酶纯化了1800倍，产率为19%，肾酶纯化了640倍，产率为10%。以Bz-Gly-His-Leu为底物时，肺酶的比活性为81 μmol/min/mg，肾酶为65 μmol/min/mg。肺酶在凝胶电泳中表现为同质，Mr = 155,000，超速离心时Sw,20 = 8.0。针对肺或肾酶产生的抗体与来自其他器官的酶发生交叉反应，但与猪酶不发生反应。在等电聚焦中，两种人酶都有一种主要形式，pI为5.2。肺制剂中还含有更多酸性形式（pI = 4 - 5），用神经氨酸酶处理后可消除。肺和肾转化酶可水解缓激肽、血管紧张素I和脑啡肽，且具有相似的动力学常数。缓激肽是最佳底物，这由其kcat/Km表明，但甲硫氨酸脑啡肽的转换数最高。Bz-Gly-His-Leu的水解受到卡托普利（SQ 14225）的竞争性抑制，以及Bz-Phe-Gly-Pro的非肽衍生物酮基ACE的非竞争性抑制。
