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

肾素是肾小球旁颗粒内形成的一水解酶，催化管紧张素原转换为管紧张素Ⅰ，即十肽。