The key difference between angiotensin 1 and 2 is that angiotensin 1 is produced from angiotensinogen by the action of renin enzyme, while angiotensinogen 2 is produced from angiotensin 1 by the action of angiotensin-converting enzyme.
Angiotensin is a peptide which acts on smooth muscle and raises blood pressure. There are three types of angiotensins: angiotensin 1, 2 and 3. Angiotensinogen transforms into angiotensin 1 through the catalysis of the renin enzyme. Angiotensin 1 converts into angiotensin 2 by the action of angiotensin-converting enzyme. It is the type of angiotensin which directly acts on blood vessels, causing constrictions and raising the blood pressure. Angiotensin 3, on the other hand, is a metabolite of angiotensin 2.
CONTENTS
1. Overview and Key Difference
2. What is Angiotensin 1
3. What is Angiotensin 2
4. Similarities Between Angiotensin 1 and 2
5. Side by Side Comparison – Angiotensin 1 vs 2 in Tabular Form
6. Summary
What is Angiotensin 1?
Angiotensin 1, also called pro-angiotensin, is a protein formed from angiotensinogen by the action of renin. It is in the inactive form and transforms into angiotensin 2 due to the cleavage action of angiotensin-converting enzyme.
Figure 01: Renin-Angiotensin Pathway
Angiotensin I has no direct biological activity. But, it acts as the precursor molecule for angiotensin 2. Angiotensin 2 level is difficult to measure. Hence, angiotensin I level is measured as a measure of renin activity by blocking the breakdown of angiotensin 1 by inhibiting plasma-converting enzyme and proteolysis by angiotensinases.
What is Angiotensin 2?
Angiotensin 2 is a protein formed from angiotensin 1 by the action of angiotensin-converting enzyme (ACE). Thus, angiotensin 1 is the precursor for angiotensin 2. The main function of angiotensin 2 is the constriction of blood vessels in order to raise blood pressure. Other than directly acting on blood vessels, angiotensin 2 carry out several functions associated with kidney, adrenal gland, and nerves. Angiotensin 2 increases the sensation for thirst and desire for salt. In the adrenal gland, angiotensin 2 stimulates the production of aldosterone. In kidneys, it increases sodium retention and alters the way the kidneys filter blood.
Figure 02: Angiotensin 1 and 2
Angiotensin 2 should be maintained at a proper level in the body. Too much of angiotensin 2 causes the retention of excess fluid in the body. In contrast, a low level of angiotensin 2 causes retention of potassium, loss of sodium, decreased fluid retention and low blood pressure, etc.
What are the Similarities Between Angiotensin 1 and 2?
- Angiotensin 1 is transformed into angiotensin 2. Therefore, angiotensin 1 is the precursor for angiotensin 2.
- The conversion of angiotensin 1 into 2 can be blocked by drugs that inhibit ACE.
What is the Difference Between Angiotensin 1 and 2?
Angiotensin 1 is a protein that acts as a precursor molecule for angiotensin 2 while angiotensin 2 is the protein that directly acts on blood vessels for constriction and raising the blood pressure. So, this is the key difference between angiotensin 1 and 2. Moreover, another significant difference between angiotensin 1 and 2 is that the angiotensin 1 is an inactive protein, while the angiotensin 2 is an active molecule.
Furthermore, renin is the enzyme that catalyzes the production of angiotensin 1 while the angiotensin-converting enzyme is the enzyme that catalyzes the synthesis of angiotensin 2. Functionally, angiotensin 1 is an important precursor for angiotensin 2 while angiotensin 2 is responsible for increasing blood pressure, body water and sodium content. Therefore, on the functional aspect, this is also a difference between angiotensin 1 and 2.
Summary – Angiotensin 1 vs 2
Angiotensin 1 and angiotensin 2 are two types of angiotensins, which are proteins. Angiotensin 1 does not have biological activity. It is in the inactive form. But, it works as the precursor molecule for the formation of angiotensin 2. On the other hand, angiotensin 2 is the active form which causes blood vessels to become narrower. It helps to maintain blood pressure and fluid balance in the body. Thus, this summarizes the difference between angiotensin 1 and 2.
Reference:
1. “Angiotensin I.” ScienceDirect Topics, Available here.
2. “Angiotensin.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 21 Aug. 2019, Available here.
Image Courtesy:
1. “2712 Renin Angiotensin System-01” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
2. “Angiotensins I and II comparison” By Fvasconcellos – Own work, after PDB entries 1N9U (angiotensin I) and 1N9V (angiotensin II) (Public Domain) via Commons Wikimedia
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