BPC-157 and TB-500 are the two peptides most often mentioned together in the research-peptide literature, and they are routinely conflated. They are not similar molecules. One is a 15-residue synthetic fragment of a gastric protein; the other is a 43-residue protein found in nearly every cell of the body, or a short fragment of it. This note compares them on the things that can be measured — sequence, size, origin, stability, analytical behaviour — and summarizes, without extrapolation, what the published laboratory work has examined.
Sequence and size
| BPC-157 | TB-500 / thymosin β4 | |
|---|---|---|
| Full name | Body Protection Compound-157 (pentadecapeptide BPC-157, “Bepecin”) | Thymosin beta-4 (Tβ4); “TB-500” is a market name applied both to full-length Tβ4 and to the synthetic fragment Ac-LKKTETQ (residues 17–23) |
| Sequence | Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val (GEPPPGKPADDAGLV) | Full Tβ4: 43 residues, N-acetylated, MW ≈ 4963 g/mol. Fragment: Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, MW ≈ 889 g/mol |
| Length | 15 amino acids | 43 (full) or 7 (fragment) |
| Molecular weight | ≈ 1419.5 g/mol | ≈ 4963 (full) / ≈ 889 (fragment) |
| CAS | 137525-51-0 | 77591-33-4 (Tβ4) |
| Origin | Synthetic; sequence derived from a region of human gastric juice protein BPC | Naturally occurring in most mammalian cells; the research material is synthetic or recombinant |
| Notable chemistry | Proline-rich, no oxidation-sensitive residues, stable in acidic conditions | Acidic, highly charged, actin-binding motif LKKTET; N-terminal acetylation |
Origin and discovery
BPC-157 was described in the early 1990s by Predrag Sikirić and colleagues at the University of Zagreb as a synthetic pentadecapeptide taken from the sequence of a larger protein isolated from human gastric juice. The great majority of the published literature on it comes from that single research group, which is worth knowing when weighing the evidence base: independent replication is thin.
Thymosin β4 was isolated from calf thymus in 1981 by Low, Hu and Goldstein and later found to be one of the most abundant intracellular proteins in mammalian cells, where its principal known function is to sequester monomeric (G-) actin and regulate cytoskeletal assembly. The 17–23 fragment, LKKTET, is the actin-binding core. Vendors selling “TB-500” may be supplying either the full protein or the fragment, and the COA — specifically the observed mass — is the only way to know which.
What the laboratory literature has examined
BPC-157: rodent models of gastrointestinal, tendon, ligament and muscle injury; effects on the nitric-oxide system and on expression of growth-factor genes in tissue; interaction with dopaminergic and serotonergic markers in animal brain. Almost all of it is in rats, from one laboratory. An Australian regulatory review in 2023 concluded there was insufficient human safety data to permit compounding.
Thymosin β4: a far broader literature from many independent groups — actin biochemistry, cell migration assays, corneal and dermal wound models in animals, cardiac models in mice, and a number of formal clinical studies of the full-length protein for eye and skin indications conducted by the company RegeneRx. None of that clinical work has led to an approved product, and none of it concerns the market material sold as “TB-500.”
These are findings in cells and animals, reported here for researchers designing experiments. They do not describe, and should not be read as describing, any effect in humans.
Analytical and handling differences
BPC-157 is an easy peptide to work with: no methionine, cysteine or tryptophan, so no oxidation problem; proline-rich, so resistant to many proteases; readily soluble in water; a single clean peak on HPLC and an unambiguous [M+H]+ at ≈ 1420 on the mass spectrum.
Full-length Tβ4 is a small protein rather than a peptide and behaves like one — it carries multiple charges, shows a distribution of charge states on electrospray MS that must be deconvoluted, and is more sensitive to adsorption on plastic and to freeze–thaw. The acetylated fragment is simpler but is a different molecule with a different mass; a COA that reports ≈ 889 Da is the fragment, and one that reports ≈ 4963 Da is the full protein.
Why they are sold together
The pairing is a market convention, not a chemical or biological one. The two compounds share nothing in sequence, origin or mechanism; what they share is that both appear in the animal wound-model literature. When they are supplied together they should be supplied as two separately labelled and separately certified vials, because the analytical requirements are different and a single purity figure for a mixture is not meaningful.
Alpha Forge Prime supplies synthetic peptides for in-vitro laboratory research only. Nothing on this page describes or recommends any use in humans or animals. Products are not drugs and have not been evaluated by the FDA.
