Angiotensin II compared with Angiogenin
Angiotensin I is converted to angiotensin II through removal of two terminal residues by the enzyme Angiotensin-converting enzyme (ACE, or kinase), which is found predominantly in the capillaries of the lung. ACE is actually found all over the body, but has its highest density in the lung due to the high density of capillary beds there. Angiotensin II acts as an endocrine, autocrine/paracrine, and intracrine hormone.ACE is a target for inactivation by ACE inhibitor drugs, which decrease the rate of angiotensin II production.
Angiotensin II increases blood pressure by stimulating the Gq protein in vascular smooth muscle cells . ACE inhibitor drugs are major drugs against hypertension.Other cleavage products of ACE, 7 or 9 amino acids long, are also known; they have differential affinity for angiotensin receptors, although their exact role is still unclear.
Angiogenin (Ang) is a small polypeptide that is implicated in angiogenesis (formation of new blood vessels) in tumor growth . However, angiogenin is unique among the many proteins that are involved in angiogenesis in that it is also an enzyme with an amino acid sequence 33% identical to that of bovine pancreatic ribonuclease (RNase) A).
Moreover, although Ang has the same general catalytic properties as RNase A - it cleaves preferentially on the 3' side of pyrimidines and follows a transphosphorylation/hydrolysis mechanism - its activity differs markedly both in magnitude and in specificity.Although angiogenin contains counterparts for the key catalytic residues of bovine pancreatic RNase A, it cleaves standard RNase substrates 105 - 106 times less efficiently than does RNase A.
Angiotensin II increases blood pressure by stimulating the Gq protein in vascular smooth muscle cells . ACE inhibitor drugs are major drugs against hypertension.Other cleavage products of ACE, 7 or 9 amino acids long, are also known; they have differential affinity for angiotensin receptors, although their exact role is still unclear.
Angiogenin (Ang) is a small polypeptide that is implicated in angiogenesis (formation of new blood vessels) in tumor growth . However, angiogenin is unique among the many proteins that are involved in angiogenesis in that it is also an enzyme with an amino acid sequence 33% identical to that of bovine pancreatic ribonuclease (RNase) A).
Moreover, although Ang has the same general catalytic properties as RNase A - it cleaves preferentially on the 3' side of pyrimidines and follows a transphosphorylation/hydrolysis mechanism - its activity differs markedly both in magnitude and in specificity.Although angiogenin contains counterparts for the key catalytic residues of bovine pancreatic RNase A, it cleaves standard RNase substrates 105 - 106 times less efficiently than does RNase A.
