Aliskiren is an inhibitor of renin. Renin, the first enzyme in the
renin–angiotensin–aldosterone system, plays a role in blood pressure control. It cleaves
angiotensinogen to
angiotensin I, which is in turn converted by
angiotensin-converting enzyme (ACE) to
angiotensin II. Angiotensin II has both direct and indirect effects on blood pressure. It directly causes arterial
smooth muscle to contract, leading to
vasoconstriction and increased blood pressure. Angiotensin II also stimulates the production of
aldosterone from the adrenal cortex, which causes the tubules of the kidneys to increase reabsorption of sodium, with water following, thereby increasing plasma volume, and thus blood pressure. Aliskiren binds to the S3bp binding site of renin, essential for its activity. ==Chemistry==