Angiotensin-Converting Enzyme (ACE, EC 3.4.15.1) is a exopeptidase that catalyses the conversion of Angiotensin I to Angiotensin II, a potent vasoconstrictor.

ACE is also involved in the inactivation bradykinin, a potent vasodilator. This explains the alternate name of kininase II (it turned out that kininase II and ACE are actually the same enzyme).

These two actions of ACE make it an ideal target in the treatment of conditions such as hypertension. Inhibition of ACE (by ACE inhibitors) results in decreased formation of Angiotensin II (a far more potent vasoconstrictor than Angiotensin I) and decreased inactivation of bradykinin.

Genetics

The ACE gene encodes 2 isozymes. The somatic ACE isozyme is expressed in many tissues, including vascular endothelial cells, renal epithelial cells, and testicular Leydig cells, whereas the germinal ACE isozyme is expressed only in sperms.

ACE is also known as:

• peptidyl dipeptidase A
• carboxycathepsin
• kininase II (kinin-kallikrein system)
• CD 143
• ACE 1

ACE II

A second ACE gene, ACE II, was identified in 2000 (Donoghue et al). ACE 2 has direct effects on cardiac function, and is expressed predominantly in vascular endothelial cells of the heart and the kidneys. Whereas ACE 1 converts Angiotensin I to Angiotensin II, which has 8 amino acids, ACE 2 converts Angiotensin I to Angiotensin[1-9], which has 9 amino acids. Whereas Angiotensin II is a potent vasoconstrictor, Angiotensin[1-9] has no effect on blood vessels but can be converted by ACE 1 to a shorter peptide, Angiotensin[1-7], which is a mild vasodilator (Boehm & Nabel 2002).

References

• Boehm M, Nabel EG. Angiotensin-converting enzyme 2--a new cardiac regulator. N Engl J Med 2002;347:1795-7. PMID 12456857.
• Donoghue M, Hsieh F, Baronas E, Godbout K, Gosselin M, Stagliano N, Donovan M, Woolf B, Robison K, Jeyaseelan R, Breitbart RE, Acton S. A novel angiotensin-converting enzyme-related carboxypeptidase (ACE2) converts angiotensin I to angiotensin 1-9. Circ Res 2000;87:E1-9. PMID 10969042.

See also

• Renin-angiotensin system
• ACE inhibitors