ABSTRACT
Angiotensin I (AngI), an inactive decapeptide generated by action of the enzyme renin on a glycoprotein substrate angiotensinogen, is converted to the active pressor octapeptide angiotensin II (AngII). The exopeptidase responsible for this conversion was first identified and isolated in plasma by Skeggs et al., who accordingly named it angiotensin-converting enzyme (ACE). ACE facilitates the removal of dipeptides and, in some cases, tripeptides from the carboxy-terminal of compatible substrates. The enzyme is a glycoprotein containing 8 to 32% carbohydrate and is heavily sialated. It has a molecular weight between 130 and 160 kDa. The components of the renin-angiotensin system, including renin and angiotensinogen mRNA, have been detected in heart. Studies in isolated cardiac myocytes and the isolated perfused heart have demonstrated local production of AngII.162 Local AngII may influence coronary and myocardial function. Furthermore, enhanced local vascular AngII production in the heart in areas of injury or inflammation may result in increased vasoconstriction or vasospasm.
