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

肾素是肾小细胞颗粒内形成的一蛋白水解酶，催化蛋白张素原转换为张素Ⅰ，即十肽。