Renin, a proteolytic enzyme formed in the granules of the juxtaglomerular apparatus cells, catalyzes conversion of the protein angiotensinogen to angiotensin I, a decapeptide.

肾素是肾小球旁体细内形成的一白水解酶，白血管紧张素原转换为血管紧张素Ⅰ，即十肽。