ANP Peptide Nomenclature: Atrial Natriuretic Peptide, ANF and the Numbered Forms

The earliest papers describe an activity in atrial extracts before the sequence was known, so the names describe the activity rather than the molecule. Atrial natriuretic factor, usually shortened to ANF, belongs to that period, as does atriopeptin, which came out of the fractionation work that separated several active atrial peptides.

As sequences were settled, ANP replaced ANF in most writing and the older names survived mainly in titles and in reviews quoting them. When I log a paper from that era I record the historical name and then write down what the sequence in the methods actually was, because the two do not always line up.

For anyone building an archive, this is the point where anp peptide nomenclature stops being a curiosity and becomes a filing decision. Every historical name I meet goes into a synonym table with the sequence it was attached to, so that a later search on one label still reaches the papers filed under another.

Numbering is the part that causes the most confusion. The full translation product is preproANP of about 151 residues, the stored granule form is the 126-residue proANP, and the circulating active peptide is the C-terminal 28 residues. Numbering in the literature usually counts from the first residue of that mature 28-residue peptide.

So ANP(1-28) is the mature form, while ANP(3-28) and ANP(4-28) are N-terminal truncations of it. Fragments from the prohormone N-terminus are numbered separately, which is why a proANP fragment and an ANP fragment can carry overlapping numbers and mean entirely different stretches of the precursor.

The trap is symmetric. A paper may write ANP and mean the 28-residue peptide, or write a numbered form and count from the precursor. I resolve it by checking whether the stated length matches 28, 126 or 151, and by reading the numbering basis out of the methods rather than out of the name. See my ANP notes on forms.

NPPA is the gene, ANP is the peptide, and anp peptide nomenclature keeps the two apart. A paper reporting NPPA expression is measuring transcript or promoter activity, not necessarily the secreted peptide, even when the discussion moves quickly from one to the other.

The same separation applies to NPPB and BNP and to NPPC and CNP. I file expression papers under the gene symbol and peptide papers under the peptide name, then cross-reference them, because conflating the two produces tables that mix transcript units with peptide units.

Prefixes do real work. hANP, rANP and mANP mark the human, rat and mouse sequences respectively, and the sequences are close but not identical. A methods section that says only ANP leaves the species to be inferred from the animal model, which is an inference I no longer make.

I also watch for papers that name a human peptide but work in a rodent, or the reverse. Those papers are usually fine, since the sequences are highly similar, but the mismatch has to be recorded because it affects any later comparison. See my ANP research notes.

Prefixes also appear on the gene symbols in database records, where capitalisation carries the species. A lower-case form marks the rodent gene and an upper-case form the human gene, so the same three letters can point to two records, and anp peptide nomenclature inherits that ambiguity from the databases.

Catalogue codes and literature names live in different systems. A code identifies one lot-defined material from one supplier, while a literature name identifies a molecular species that any number of materials might match. The mapping between them is a claim, and like any claim it needs the sequence behind it.

In my notes a catalogue entry is always stored with the lot, the stated sequence and the date checked. That is the only anp peptide nomenclature habit that has reliably survived contact with older papers, where a code from a defunct catalogue is often the sole identifier left.

I also keep a line for how the material was described by the source, since descriptive labels drift between catalogues and between revisions of the same catalogue. When one code maps to two different descriptions in my own records, I hold the newer one as provisional until a sequence confirms it.

The working method is short: locate the name, find the sequence or the fragment boundaries in the methods, check the species, and only then file the paper. Where a paper gives none of those, I file it under the name and mark the molecule unresolved rather than guessing from the title.