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ACE inhibitor (Angiotensin Converting Enzyme Inhibitor) Types, Indications, Effect

Angiotensin-converting-enzyme inhibitor (ACE inhibitor) is a pharmaceutical drug used primarily for the treatment of hypertension (elevated blood pressure) and congestive heart failure. This group of drugs causes relaxation of blood vessels as well as a decrease in blood volume, which leads to lower blood pressure and decreased oxygen demand from the heart. They inhibit the angiotensin-converting enzyme, an important component of the renin-angiotensin system.

Types

ACE inhibitors are easily identifiable by their common suffix, ‘-pril’. ACE inhibitors can be divided into three groups based on their molecular structure:

Sulfhydryl-containing agents

Captopril
Zofenopril

Dicarboxylate-containing agents

This is the largest group, including:

Enalapril
Ramipril
Quinapril
Perindopril
Lisinopril
Benazepril
Imidapril
Trandolapril
Cilazapril

Phosphonate-containing agents

Fosinopril is the only member of this group

Naturally occurring

A comprehensive resource on anti-hypertensive peptides is available in form of a database. It contains around 1700 unique antihypertensive peptides
Arfalasin (HOE 409) is an angiotensin antagonist.

Dairy products

Casokinins and lactokinins, breakdown products of casein and whey, occur naturally after ingestion of milk products, especially cultured milk. Their role in blood pressure control is uncertain.
The lactotripeptides Val-Pro-Pro and Ile-Pro-Pro produced by the probiotic Lactobacillus helveticus or derived from casein have been shown to have ACE-inhibiting and antihypertensive functions. In one study, L. helveticus PR4 was isolated from Italian cheeses.

Types overall………………………………………………………………….

ACE inhibitors (“-pril”)	Sulfhydryl-containing: Captopril Rentiapril Zofenopril Dicarboxylate-containing: Enalapril Benazepril Cilazapril Delapril Imidapril Lisinopril (+HCT) Moexipril Perindopril (+indapamide) Quinapril (+HCT) Ramipril Spirapril Temocapril Trandolapril Phosphonate-containing: Ceronapril Fosinopril (+HCT) Other/ungrouped: Alacepril

Mechanism of action

Normally, angiotensin I is converted to angiotensin II by an angiotensin-converting enzyme (ACE). Angiotensin II constricts blood vessels, increasing blood pressure. Enalaprilat, the active metabolite of enalapril, inhibits ACE. Inhibition of ACE decreases levels of angiotensin II leading to less vasoconstriction and decreased blood pressure.

There are two isoforms of ACE: the somatic isoform, which exists as a glycoprotein comprised of a single polypeptide chain of 1277; and the testicular isoform, which has a lower molecular mass and is thought to play a role in sperm maturation and binding of sperm to the oviduct epithelium. Somatic ACE has two functionally active domains, N and C, which arise from tandem gene duplication. Although the two domains have high sequence similarity, they play distinct physiological roles. The C-domain is predominantly involved in blood pressure regulation while the N-domain plays a role in hematopoietic stem cell differentiation and proliferation. ACE inhibitors bind to and inhibit the activity of both domains, but have the much greater affinity for an inhibitory activity against the C-domain. Enalaprilat, the principal active metabolite of enalapril, competes with ATI for binding to ACE and inhibits and enzymatic proteolysis of ATI to ATII. Decreasing ATII levels in the body decreases blood pressure by inhibiting the pressor effects of ATII as described in the Pharmacology section above. Enalapril also causes an increase in plasma renin activity likely due to a loss of feedback inhibition mediated by ATII on the release of renin and/or stimulation of reflex mechanisms via baroreceptors. Enalaprilat’s affinity for ACE is approximately 200,000 times greater than that of ATI and 300-1000 times greater than that enalapril.

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Indications

Diabetic Nephropathies
High blood pressure (Hypertension)
Diabetic kidney disease
High blood pressure
Left ventricular dysfunction
Heart failure
Hypertensive emergency
Alport syndrome
Symptomatic congestive heart failure
Asymptomatic left ventricular dysfunction
Also for the treatment of essential or renovascular hypertension and symptomatic congestive heart failure. It may be used alone or in combination with thiazide diuretics.