Angiotensin i

Angiotensin was first described in 1940 by I.H. Page. He found that the angiotensinogen formed in the liver is a substrate for the enzyme renin, which is derived from the kidney. As a result of an enzymatic reaction, a substance was found which leads to vasoconstriction and an increase in blood pressure.

Angiotensin I belongs to the group of angiotensins, which form a group of peptide hormones belonging to the tissue hormones, which are formed by enzymatic cleavage by various peptidases from angiotensinogen of the liver.

Thus angiotensin I is formed enzymatically by the peptidase /en/internal-medicine/ace-136622" title="Ace}reninfrom angiotensinogen. Angiotensin I itself is largely inactive. In the presence of the angiotensin converting enzyme (ACE), angiotensin I is cleaved into the octapeptide angiotensin II, which is responsible for the vasocontrictive effect.

According to their chemical structure, ACE inhibitors are angiotensin I - dipeptide or tripeptide analogues of the C-terminal amino acid sequence of angiotensin I. They are all acids with at least one free carboxyl group required for binding with the catalytic centre of the ACE.

A hitherto largely unexplored further activation pathway emanating from angiotensin I is its cleavage in the presence of the angiotensin converting enzyme type 2 and further peptidases to the heptapeptide angiotensin, a molecule which interacts with a hitherto unknown angiotensin receptor.