Abstract
—ACE2, the first known human homologue of angiotensin-converting enzyme (ACE), was identified from 5′ sequencing of a human heart failure ventricle cDNA library. ACE2 has an apparent signal peptide, a single metalloprotease active site, and a transmembrane domain. The metalloprotease catalytic domains of ACE2 and ACE are 42% identical, and comparison of the genomic structures indicates that the two genes arose through duplication. In contrast to the more ubiquitous ACE, ACE2 transcripts are found only in heart, kidney, and testis of 23 human tissues examined. Immunohistochemistry shows ACE2 protein predominantly in the endothelium of coronary and intrarenal vessels and in renal tubular epithelium. Active ACE2 enzyme is secreted from transfected cells by cleavage N-terminal to the transmembrane domain. Recombinant ACE2 hydrolyzes the carboxy terminal leucine from angiotensin I to generate angiotensin 1-9, which is converted to smaller angiotensin peptides by ACE in vitro and by cardiomyocytes in culture. ACE2 can also cleave des-Arg bradykinin and neurotensin but not bradykinin or 15 other vasoactive and hormonal peptides tested. ACE2 is not inhibited by lisinopril or captopril. The organ- and cell-specific expression of ACE2 and its unique cleavage of key vasoactive peptides suggest an essential role for ACE2 in the local renin-angiotensin system of the heart and kidney. The full text of this article is available at http://www.circresaha.org.
摘要—ACE2是已知的第一个人类同源物,与肾素转化酶(ACE)相似,它是从人类心力衰竭心室cDNA文库的5'序列中鉴定出来的。ACE2具有明显的信号肽、单个金属蛋白酶活性位点和跨膜域。ACE2和ACE的金属蛋白酶催化结构域相似度为42%,基因组结构的比较表明这两个基因是通过复制产生的。与更广泛存在的ACE相比,23种人体组织中只在心脏、肾脏和睾丸中发现ACE2转录本。免疫组织化学显示ACE2蛋白主要存在于冠状和肾内血管内皮和肾小管上皮中。转染细胞分泌活性ACE2酶通过跨膜域前的剪切而分泌。重组ACE2水解血管紧张素I的羧基端亮氨酸,生成血管紧张素1-9,这被ACE在体外和心肌细胞培养中转化为更小的血管紧张素肽。ACE2还可以水解des-Arg bradykinin和神经肽,但不能水解bradykinin或其他15种测试的血管活性和激素肽。ACE2不受lisinopril或captopril的抑制。ACE2的器官和细胞特异性表达以及其对关键血管活性肽的独特水解作用,表明ACE2在心脏和肾脏的局部肾素-血管紧张素系统中具有重要作用。本文的全文可在http://www.circresaha.org上获得。