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[Biochemistry](https://durgical.com/en/biochemistry/) · Enzyme

# Angiotensin-converting enzyme (ACE)

ACE makes angiotensin II, which narrows vessels, and breaks down bradykinin, which widens them. ACE inhibitors block it.

Updated 2026-11-01

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## Key facts

- A zinc peptidase that clips two amino acids off the C-terminal end of peptides.
- Renin–angiotensin system: angiotensin I (inactive) → angiotensin II, a strong vasoconstrictor.
- The same enzyme (kininase II) inactivates bradykinin, a vasodilator; it also cuts substance P and enkephalins.
- It sits on the outer surface of cells, anchored by one pass through the membrane; a cleaved soluble form circulates in plasma.

**Also called**
Kininase II, Dipeptidyl carboxypeptidase I

**EC number**
[3.4.15.1](https://www.enzyme-database.org/query.php?ec=3.4.15.1)

**Genes**
ACE

**Structure (PDB)**
[1UZE](https://www.rcsb.org/structure/1UZE)

## Structure

- The somatic form has two catalytic domains (N and C), each with its own active site and zinc ion; chloride activates it.
- Structure 1UZE is the testicular form, which has a single domain, holding enalaprilat in the active site next to the zinc.

## Regulation

- Chloride ions strongly activate it.
- Angiotensin II production is mostly set upstream, by how much renin the kidney releases.

## Inhibitors and toxins

- ACE inhibitors (enalapril): enalapril is a prodrug; hydrolysis of its ester gives enalaprilat, the active inhibitor.

## Clinical notes

- Less angiotensin II widens vessels and lowers aldosterone: ACE inhibitors treat high blood pressure and heart failure, and protect the kidney in diabetes.
- A persistent dry cough is reported with all ACE inhibitors and is usually attributed to bradykinin that is no longer broken down; angioedema (face, lips, tongue, larynx) is rare.
- Potassium can rise, especially with kidney disease or potassium-sparing drugs.
- These drugs are stopped as soon as pregnancy is detected: they can harm the fetus.

## Drugs that act here

- [Enalapril](https://durgical.com/en/pharmacology/enalapril/)
- [Captopril](https://durgical.com/en/pharmacology/captopril/)
- [Lisinopril](https://durgical.com/en/pharmacology/lisinopril/)
- [Ramipril](https://durgical.com/en/pharmacology/ramipril/)
- [Perindopril](https://durgical.com/en/pharmacology/perindopril/)

## Related conditions

- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)
- [Heart failure](https://durgical.com/en/conditions/heart-failure/)
- [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/)
- [Hypertensive heart disease](https://durgical.com/en/conditions/hypertensive-heart-disease/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which two peptides does ACE handle, with opposite effects on vessels?

It makes angiotensin II (vasoconstrictor) from angiotensin I and inactivates bradykinin (vasodilator).

## Which metal sits in the ACE active site?

Zinc; ACE inhibitors such as enalaprilat bind next to it.

## Why is enalapril called a prodrug?

It is inactive until its ester is cut, giving enalaprilat, the form that inhibits ACE.

## Which ACE-inhibitor adverse effect is linked to bradykinin?

Dry cough and, rarely, angioedema.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [ACE: Angiotensin-converting enzyme (human)](https://rest.uniprot.org/uniprotkb/P12821.txt) (UniProt, 2026); [1UZE: Complex of the anti-hypertensive drug enalaprilat and the human testicular angiotensin I-converting enzyme](https://www.rcsb.org/structure/1UZE) (RCSB Protein Data Bank, 2026); [ENALAPRIL MALEATE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a88902bd-742f-4ea6-b625-cc9df1709efc) (DailyMed, US National Library of Medicine, 2026); [Enalapril: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a686022.html) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/biochemistry/enzymes/angiotensin-converting-enzyme/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/enzymes/angiotensin-converting-enzyme/