Angiotensinogen is an α2-globulin precursor from which all other angiotensin peptides are derived. Angiotensinogen is produced primarily by the liver, but angiotensinogen mRNA has also been detected in adipocytes, the kidney, regions of the brain, the adrenal gland, the heart and blood vessels. Renin, an enzyme synthesized by juxtaglomerular cells of the renal cortex, cleaves angiotensinogen to the decapeptide, angiotensin I. The conversion of angiotensinogen to angiotensin I is the rate-limiting step in the production of biologically active angiotensin peptides.