Compound monograph
Thymosin beta-4
Thymosin beta-4 is an N-terminally acetylated peptide originally isolated from a thymic tissue fraction and subsequently characterized as a G-actin-sequestering peptide.
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Identity & nomenclature
Thymosin beta-4 is an N-terminally acetylated peptide originally isolated from a thymic tissue fraction and subsequently characterized as a G-actin-sequestering peptide.
Timbetasin is the INN for thymosin beta-4. TB-500 is not this molecule. That name designates a distinct seven-residue fragment, carried separately in PubChem as CID 62707662 with a molecular mass of approximately 889 daltons, against 4963.5 daltons for the full-length peptide described here; the two records also carry different UNII identifiers. Material sold as TB-500 should be identified against the intended species rather than against this record. The PubChem synonym set for this record also includes a carbon-13-labelled internal standard used in mass spectrometry; that labelled compound has a different exact mass and must not be used as an identity reference for unlabelled material.
Canonical name: Timbetasin.
Declared aliases and development codes: Thymosin b4, Tbeta4, TB4.
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Molecular properties
| Molecular formula | C212H350N56O78S |
|---|---|
| Molecular mass | 4963.5 Da |
| CAS Registry Number | 77591-33-4 |
| PubChem CID | 16132341 |
| UNII | 2D5MRE3SSY |
| One-letter sequence | SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES |
| Three-letter sequence | Ser–Asp–Lys–Pro–Asp–Met–Ala–Glu–Ile–Glu–Lys–Phe–Asp–Lys–Ser–Lys–Leu–Lys–Lys–Thr–Glu–Thr–Gln–Glu–Lys–Asn–Pro–Leu–Pro–Ser–Lys–Glu–Thr–Ile–Glu–Gln–Glu–Lys–Gln–Ala–Gly–Glu–Ser |
| Terminal groups | N-terminal acetylation; Free C-terminal carboxyl |
Forty-three residues of the mature chain, numbered from Ser1; UniProt P62328 lists the same chain as positions 2-44 because its initiator methionine is removed. Ser1 is N-acetylated and Ser43 carries a free carboxyl, as encoded by PubChem CID 16132341; the one-letter string does not show the acetyl group. Positions 17-23, LKKTETQ, are the fragment described in the TB-500 record. Summing the forty-three residues, removing forty-two waters and adding the acetyl increment C2H2O gives C212H350N56O78S and 4963.51 Da, reproducing the recorded formula.
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Structural characteristics
The peptide was isolated from thymosin fraction 5, a mixture of polypeptides, alongside thymosin alpha-1 and polypeptide beta-1. The source review records that none of the isolated peptides proved to be thymic hormones. G-actin sequestration was identified in 1990. The peptide is reported to be unstructured in isolation and to fold into a stable conformation on binding G-actin. Related beta-thymosins have been isolated and sequenced from several species.
Terminal features: N-terminal acetylation, Free C-terminal carboxyl.
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Molecular targets & mechanisms
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Analytical considerations
The single sulfur atom corresponds to one sulfur-containing residue; oxidized forms of the peptide are described separately in the literature and are a relevant degradation consideration. The N-terminal acetyl group is part of the declared identity. Reference material should be confirmed as unlabelled, because the PubChem record groups a carbon-13-labelled standard under the same identifier.
Disagreements and mix-ups
Points where sources disagree about this compound's identity, or where a name or form is easily confused with another, as noted in this record. The discrepancy register quotes the passage for each one.
Often mixed up · Name or substance
TB-500 is not thymosin beta-4
What the studies reported
Each finding describes one cited study in its stated model. These observations are specific to that study and do not establish effects in other settings.
Cell and tissue studies
Thymosin-β4, meprin-α and prolyl oligopeptidase enzymatic assay
The study observed Ac-SDKP release when thymosin-β4 was incubated with both meprin-α and prolyl oligopeptidase, but no release with either enzyme alone in an in-vitro enzymatic assay.
Reference [5]Rat kidney homogenates
In rat kidney homogenates, the study reported significant Ac-SDKP release from thymosin-β4 that was blocked by the meprin-α inhibitor actinonin.
Reference [5]Kidney cortex homogenates
In kidney cortex homogenates, the study observed time-dependent Ac-SDKP generation in the presence of exogenous thymosin-beta4 and significant inhibition of that generation by prolyl oligopeptidase inhibitors.
Reference [6]
Animal studies
Wild-type mice following unilateral ureteral obstruction
In wild-type mice following unilateral ureteral obstruction, the study reported reduced late fibrosis with Tβ4 alone and increased fibrosis when Tβ4 was combined with a prolyl oligopeptidase inhibitor.
Reference [7]PAI-1 knockout mice following unilateral ureteral obstruction
In PAI-1 knockout mice following unilateral ureteral obstruction, the study reported that both the profibrotic effects of Tβ4 plus prolyl oligopeptidase inhibition and the late reparative effects of Tβ4 alone were absent.
Reference [7]
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Verified bibliography
Cited studies by type
The 7 papers this record cites, counted by the kind of work each reports. A count is the size of this record's selection, not of the research that exists, and says nothing about results, safety, effectiveness or approval.
A paper can report more than one kind of work. Each count opens those papers in the bibliography. Compare every record on the Evidence Map.
Reference 1
currentReference 2
Actin dynamics.Pollard TD, Blanchoin L, Mullins RD
Journal of cell science · 2001-01 · Journal Article
currentReference 3
Thymosin beta4 and its posttranslational modifications.Hannappel E
Annals of the New York Academy of Sciences · 2010-04 · Review
currentReference 4
The beta-thymosin enigma.Sun HQ, Yin HL
Annals of the New York Academy of Sciences · 2007-05-10 · Review
currentReference 5
The anti-inflammatory peptide Ac-SDKP is released from thymosin-β4 by renal meprin-α and prolyl oligopeptidase.Kumar N, Nakagawa P, Janic B, Romero CA, Worou ME, Monu SR, Peterson EL, Shaw J, Valeriote F, Ongeri EM, Niyitegeka JM, Rhaleb NE, Carretero OA
American journal of physiology. Renal physiology · 2016-03-09 · Journal Article
currentReference 6
Prolyl oligopeptidase is involved in release of the antifibrotic peptide Ac-SDKP.Cavasin MA, Rhaleb NE, Yang XP, Carretero OA
Hypertension (Dallas, Tex. : 1979) · 2004-03-22 · Journal Article
currentReference 7
Thymosin β4 and its degradation product, Ac-SDKP, are novel reparative factors in renal fibrosis.Zuo Y, Chun B, Potthoff SA, Kazi N, Brolin TJ, Orhan D, Yang HC, Ma LJ, Kon V, Myöhänen T, Rhaleb NE, Carretero OA, Fogo AB
Kidney international · 2013-06-05 · Journal Article
current
Study models of these references
What kind of experiment each cited paper reports, taken from its abstract unless marked. Not a summary of results.
| Reference | Study models |
|---|---|
| Hannappel E 2007 | Review article |
| Pollard TD et al. 2001 | No abstract available; study type not determined |
| Hannappel E 2010 | Review article |
| Sun HQ et al. 2007 | Review article |
| Kumar N et al. 2016 | Study models reported: in vitro; animal (rat) · from the abstract |
| Cavasin MA et al. 2004 | Study models reported: in vitro; animal (rat) · from the abstract |
| Zuo Y et al. 2013 | Study models reported: animal (mouse) · from the abstract |
Compare
Record history
Published 2026-09-04.
- : Identity and nomenclature, Sequence and structure
- : References
- : Identity and nomenclature
- : References
Each entry names the parts of this record that changed on that date. Changes to links between records and to catalogue links are not listed. This history covers the tracked record fields; study findings are not listed here.
Cite this record: Purely Peptides Research Library. Thymosin beta-4. Published 2026-09-04; updated 2026-10-14. https://purelypeptides.org/research/compounds/thymosin-beta-4/
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Methodology & citation verification
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