Key facts
- Systematic rule
- Residues named as acyl groups (-yl), last residue keeps its full name
- Order
- Always N-terminus to C-terminus
- Sequence names
- Three-letter (Gly-His-Lys) or one-letter (GHK)
- Fragment names
- Parent and residue range, e.g. GHRH (1-29)
- Nonproprietary names
- WHO INN stems, e.g. -morelin, -relin, -tide
- Governing bodies
- IUPAC-IUB (chemistry), WHO (INN)
Five Ways Peptides Are Named
Peptide names come from five overlapping systems, and one compound will often carry names from several of them at once.
| System | How it works | Example |
|---|---|---|
| Systematic (IUPAC-IUB) | Residues listed as acyl groups from N- to C-terminus | glycyl-L-histidyl-L-lysine |
| Sequence notation | Three-letter or one-letter codes | Gly-His-Lys, GHK |
| Trivial name | Historical or descriptive name | Glutathione |
| Code name | Laboratory or company designation | BPC-157, SS-31, PT-141, CJC-1295 |
| Nonproprietary name (INN) | Official generic name with a WHO stem | Sermorelin, tesamorelin, bremelanotide |
It helps to know which system a name came from, because that tells you how much structure the name gives away. A systematic or sequence name pins down the whole chain. A code name tells you next to nothing. If you need the basics of what is being named, start with What Is a Peptide?.
How Do Systematic Peptide Names Work?
A systematic name lists every residue in order, starting at the N-terminus, and turns each name except the last into an acyl form ending in -yl [1].
The rule mirrors the chemistry. Each residue other than the C-terminal one gives its carboxyl group to a peptide bond, so it gets named as an acyl substituent: glycine becomes glycyl, histidine becomes histidyl, lysine becomes lysyl. The C-terminal residue still has its carboxyl group, so it keeps its full name. Each chiral residue also gets an L- or D- prefix. Glycine, which isn't chiral, gets neither.
- Gly-His-Lys: glycyl-L-histidyl-L-lysine
- Lys-Pro-Val (KPV): L-lysyl-L-prolyl-L-valine
- Glutathione: gamma-L-glutamyl-L-cysteinylglycine, where gamma marks the side-chain link [2]
Some acyl forms break the pattern: tryptophan becomes tryptophyl, cysteine cysteinyl, glutamine glutaminyl and asparagine asparaginyl. Full names get long fast, which is why you mostly see systematic names for short peptides, in registries and on formal documents.
Sequence Notation as a Name
Once a peptide runs past a few residues, sequence-based peptide names take over: people just use the sequence, written in standard codes, as the working name.
Three-letter symbols joined by hyphens (Gly-Glu-Pro-Pro...) are easy to read, and each hyphen stands for a peptide bond. One-letter codes are compact, so databases favor them; BPC-157, for instance, is GEPPPGKPADDAGLV [1][3]. Terminal groups and modifications go on as prefixes and suffixes: H- for a free amino terminus, -OH for a free acid, -NH2 for an amide, Ac- for an acetyl cap. For a side-by-side comparison, see One-Letter vs. Three-Letter Amino Acid Codes.
Fragment and Analogue Names
When a peptide comes from a larger parent, its name often gives the parent plus the stretch of residues it covers.
Take sermorelin, written GRF (1-29) NH2. It matches residues 1 to 29 of growth hormone-releasing hormone, with an amidated C-terminus. KPV sometimes appears as alpha-MSH (11-13). Substitutions are written as the new residue and its position, sometimes with the original residue too, so an analogue's name can spell out exactly how it differs from the parent. Additions at the ends are named as groups. Tesamorelin, for example, is the full 44-residue GHRH sequence with an N-terminal trans-3-hexenoyl group. The Sermorelin and Tesamorelin pages show those structures.
Trivial and Code Names
Among peptide names, trivial names and code names are the quickest way to identify a compound. What they won't do is tell you much, if anything, about structure.
Glutathione, carnosine and insulin are trivial names. They predate the systematic rules and survive because everyone uses them. Code names come from whichever lab or company first described the compound. BPC-157 stands for Body Protection Compound; SS-31, PT-141 and CJC-1295 are likewise research designations. The risk with code names is that nobody controls them, so one name can end up on different materials. TB-500 shows the problem clearly: it's used for full-length thymosin beta-4 and also for a short fragment of it. That's why the TB-500 page insists on checking the stated sequence.
Peptide names on a label do not establish what a material is. Identity is set by the full structure, including sequence and terminal groups, and confirmed by analytical data such as mass spectrometry.
How Do Nonproprietary (INN) Names Work?
International Nonproprietary Names (INNs) are official generic names chosen by the World Health Organization. They share stems, so related substances end up with related names [4].
WHO's stem guide links endings to pharmacological families [5]. Three come up a lot in peptide names:
- -relin: pituitary hormone-release stimulating peptides.
- -morelin: growth hormone release-stimulating peptides; the WHO list includes ipamorelin, sermorelin and tesamorelin.
- -tide: peptides and glycopeptides, with sub-groups such as -melanotide (melanocortin receptor agonists, including bremelanotide).
That's how PT-141 and bremelanotide can name the same molecule: one is a code, the other an INN. GHK-Cu, likewise, appears in the WHO list as prezatide copper acetate. Keep in mind that an INN stem points to a family, not a full structure, and WHO advises against building trade names from INN stems [4].
Why Naming Matters for Documentation
All of this matters for one practical reason: an analytical document has to tie a compound's peptide names to exactly one structure.
A good product record or Certificate of Analysis gives the common name, any synonyms (code name, INN), the full sequence, terminal groups and salt form, so that every name leads back to the same molecule. If something doesn't line up, say a code name with no sequence, ask for more information. Terms used on these documents are defined in the peptide glossary, and the Compound Library lists each Vinnix compound alongside its synonyms.
FAQFrequently asked questions
How do you name a peptide from its sequence?
Systematic peptide names start at the N-terminus. Name each residue as an acyl group ending in -yl, and give the last, C-terminal residue its full name. So Gly-His-Lys becomes glycyl-L-histidyl-L-lysine. Each chiral residue gets L- or D-, and terminal modifications such as an acetyl group or a C-terminal amide are named separately.
Why do peptide names end in -yl?
It marks a residue that has handed its carboxyl group over to a peptide bond, so the residue is named as an acyl substituent of the next one. Only the C-terminal residue still has a free carboxyl group. That's why it is the one residue that keeps its normal amino acid name.
What does -tide mean at the end of a drug name?
In WHO International Nonproprietary Names, -tide is the stem for peptides and glycopeptides. Narrower sub-stems mark particular families; -melanotide, for example, covers melanocortin receptor agonists. The stem tells you a substance belongs to a peptide family. It doesn't tell you the exact sequence.
Are PT-141 and bremelanotide the same compound?
Yes. PT-141 is the research code name, and bremelanotide is the International Nonproprietary Name for the same cyclic heptapeptide. PubChem lists one formula for it, C50H68N14O10. The two names simply come from different naming systems; they don't describe different molecules.
What does the number in BPC-157 mean?
BPC stands for Body Protection Compound. The 157 is a designation from the original research, not a residue count or a mass; BPC-157 actually has 15 amino acids. Code names like this are handy labels for identifying a compound, but they say nothing reliable about structure.
Why do some peptides have numbers in brackets, like (1-29)?
In peptide names, the numbers in brackets give the residue range of the parent peptide or protein that a fragment covers. GHRH (1-29) means residues 1 through 29 of growth hormone-releasing hormone, counting from the N-terminus. Sermorelin is written that way because it matches that segment, with an amidated C-terminus.
REFScientific references
-
IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). Nomenclature and symbolism for amino acids and peptides. Recommendations 1983. Eur J Biochem. 1984;138(1):9-37. PubMed 6692818
nomenclature standard -
IUPAC-IUB Commission on Biochemical Nomenclature. A one-letter notation for amino acid sequences. Tentative rules. J Biol Chem. 1968;243(13):3557-3559. PubMed 5658538
nomenclature standard -
Kopp-Kubel S. International Nonproprietary Names (INN) for pharmaceutical substances. Bull World Health Organ. 1995;73(3):275-279. PubMed 7614659
policy review -
World Health Organization. The use of stems in the selection of International Nonproprietary Names (INN) for pharmaceutical substances. WHO/EMP/RHT/TSN/2018.1. Geneva: WHO; 2018. (Not indexed in PubMed; document retrieved from WHO and checked.) Source
nomenclature guidance (WHO)
Research Library: Peptide Fundamentals