Natriuretic Peptide ANP: The Family and the Naming

By What Peptides Editorial Team · Updated 2026-09-14 · Part of Peptide Structure, Classification & Scientific Terminology

ANP stands for atrial natriuretic peptide, and that abbreviation is only one member of a small family. The family is built on a single shared structural feature, a 17-residue ring closed by one disulfide bond, and the members differ in where they are made, how long they are, and which receptor they prefer. The naming is partly anatomical and partly historical: ANP and BNP were named for the tissue or the extract that yielded them, CNP for its type, and DNP for the snake venom it was isolated from. This page is about the family and about that naming. The structure of ANP on its own is treated in a separate article, and the two are written to be read as a pair rather than as alternatives.

Two further naming problems sit on top of the biology. The first is between the peptide and its fragments: each member is made as a longer precursor and cut into a signalling piece and an N-terminal piece, and both pieces end up in blood. The second is between the analytes a laboratory measures, because an assay for BNP and an assay for NT-proBNP measure different molecules with different half-lives and different clearance routes, so their numbers are not interchangeable. Our peptide structure and classification reference sets out how such families are grouped; this page explains why the names on a report are not synonyms for one another.

The family: source, length and receptor preference

ANP is encoded by NPPA and is made mainly in atrial myocytes, where it is stored in secretory granules and released in response to atrial stretch. The mature hormone is 28 residues. BNP comes from NPPB, and although it was named for brain tissue where it was first detected, the ventricle is the dominant source in adults; the mature form is 32 residues. CNP, from NPPC, is made in endothelium, in the central nervous system and in growth-plate cartilage, and circulates as CNP-22 with a longer CNP-53 form also described. All three share the 17-residue ring, and the ring is the part the receptors recognise.

Two further names belong in any family table. Urodilatin is an N-terminally extended form of ANP, 32 residues, produced in the kidney from the same precursor by different processing, and it acts locally rather than as a circulating hormone. DNP, the dendroaspis natriuretic peptide, was isolated from green mamba venom and carries a 17-residue ring with a much longer C-terminal tail; it is a research probe rather than a human hormone, which is why it appears in the literature on receptors rather than in physiology. Receptors divide the family cleanly: NPR-A is the guanylyl cyclase receptor preferred by ANP and BNP, NPR-B is the one preferred by CNP, and NPR-C binds all three while acting mainly as a clearance receptor.

Precursor processing and what circulates

Every member is made as a preproprotein. ANP is translated as a 151-residue preproprotein; removal of the signal peptide leaves a 126-residue prohormone that is stored in atrial granules and cleaved on release, with corin described as the cardiac protease responsible, giving an N-terminal fragment and the 28-residue C-terminal hormone. BNP follows the same pattern: the prohormone is cleaved into an inactive N-terminal fragment of 76 residues and the active 32-residue C-terminal peptide, and the prohormone is reported to be glycosylated in a region that affects how antibodies recognise it. CNP is processed from proCNP through a 53-residue intermediate to the 22-residue active peptide.

Clearance is what makes the fragments behave differently once they are in blood. Two routes remove the active peptides: receptor-mediated uptake through NPR-C followed by degradation inside the cell, and proteolysis by neprilysin, a cell-surface metalloprotease that cleaves within the ring. The N-terminal fragments are not substrates for neprilysin and depend more on renal clearance, so they persist longer. Reported half-lives follow that logic: ANP is cleared within minutes, BNP is reported in the range of about twenty minutes, and NT-proBNP is reported at one to two hours. Different stability, different clearance route, and therefore different behaviour in a sample tube as well as in a patient.

The structural point underneath all of this is the ring itself. The disulfide closes a 17-residue loop between two conserved cysteines, and disrupting it is reported to abolish activity at the signalling receptors. The N-terminal and C-terminal extensions differ between members and tune potency, receptor preference and clearance rather than defining recognition.

Assay forms: why BNP and NT-proBNP are measured differently

The two analytes are different molecules made from the same precursor. BNP is the active 32-residue peptide, subject to both clearance routes above, with a short reported half-life and a structure that neprilysin can cut. NT-proBNP is the inactive 76-residue N-terminal fragment, is not a neprilysin substrate, clears largely through the kidney and persists longer. In practice that gives NT-proBNP a longer window in a collected specimen and less variability over hours, and it gives BNP a closer relationship to the moment of release.

Assay design adds a second layer. Antibody pairs target different epitopes, and some BNP assays cross-react with the precursor and with fragments, so a measured value can include species other than the 32-residue peptide. Standardisation differs between manufacturers, which is why reference intervals are quoted against a named method rather than in the abstract. Sample handling differs too: both analytes are measured in EDTA plasma, and the active peptide degrades faster in a collected tube than the N-terminal fragment does. Reports quote the same unit in two forms, picograms per millilitre and nanograms per litre, which are numerically equal, and this is descriptive laboratory information rather than clinical guidance. For how a research material is documented before any of this measurement happens, see how peptide reference materials are catalogued.

For readers who arrived here from the naming question, the split is worth stating: the 28-residue structure of ANP itself covers sequence and ring geometry, while this page covers the family, the receptor preferences and the two analytes that carry the family name in laboratory reports.

This page is part of the Peptide Structure, Classification & Scientific Terminology guide.