Angiotensin I (1-9), also known as Des-Leu10-Angiotensin I, is a nine-residue peptide with the sequence Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His (DRVYIHPFH).

It is generated from Angiotensin I through removal of the C-terminal Leu10 residue and is studied as part of the alternative, counter-regulatory branches of the renin–angiotensin system.

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Formation Through ACE2-Dependent Processing

ACE2 can remove the C-terminal leucine from Angiotensin I to generate Angiotensin-(1-9). The resulting nonapeptide can subsequently undergo additional processing, including conversion toward Angiotensin-(1-7).

This places Angiotensin-(1-9) at a different branch point from the classical ACE-dependent formation of Angiotensin II.

Cardiovascular Research Context

Experimental studies have associated Angiotensin-(1-9) with cardiovascular remodeling and AT2 receptor-dependent responses. These effects remain less extensively characterized than the classical Angiotensin II–AT1R pathway.

We recommend treating Angiotensin-(1-9) as its own molecular entity rather than grouping it with Angiotensin A or Angiotensin II simply because the sequences are closely related.

A Single-Residue Processing Difference

Human Angiotensin I is DRVYIHPFHL. Angiotensin-(1-9) removes only the terminal Leu:

DRVYIHPFHL → DRVYIHPFH

This small structural change creates a distinct substrate and signaling context, making the pair useful for peptide-processing studies.

Frequently Asked Questions

Is Angiotensin I (1-9) the same as Angiotensin A?

No. Angiotensin-(1-9) has the sequence DRVYIHPFH. Angiotensin A has the sequence ARVYIHPF.

How is Angiotensin-(1-9) generated?

ACE2 can remove Leu10 from Angiotensin I to produce the nine-residue peptide.

Research Use Only.