Ac-SDKP (Thymosin Beta-4 Fragment 1-4) Capsules
60 hard gelatin capsules, each with 500 mcg of N-acetyl-Ser-Asp-Lys-Pro, the N-terminal tetrapeptide of thymosin beta-4, in a cellulose filler. Tested in the manufacturer’s own laboratory.
| Compound | Ac-SDKP (Goralatide; N-acetyl-Ser-Asp-Lys-Pro (thymosin beta-4 fragment 1-4)) |
|---|---|
| CAS number | 127103-11-1 |
| Molecular formula | C20H33N5O9 |
| Form | Hard gelatin capsules containing the active substance blended with microcrystalline cellulose, packed in a sealed bottle |
| Storage, sealed | Store at room temperature (15–25 °C) in the tightly closed original container, dry and protected from light |
| Format | Capsules in a sealed bottle |
Sizes and lots
- 500 mcg × 60 · 1 bottle — $148.99
- 500 mcg × 60 · Kit of 10 — $1324.52
Ac-SDKP is the tetrapeptide N-acetyl-Ser-Asp-Lys-Pro, also called goralatide. Its sequence is the first four residues of thymosin beta-4, from which the enzyme prolyl oligopeptidase can release it. This listing is a bottle of 60 hard gelatin capsules, each holding 500 mcg of the peptide blended with microcrystalline cellulose. Research on Ac-SDKP began with the regulation of blood-forming stem cells and later turned to its breakdown by angiotensin-converting enzyme and its antifibrotic effects in rats.
Names, structure and specificity
One molecule turns up under several names. Ac-SDKP and AcSDKP are abbreviations of the acetylated sequence, goralatide is the name given on the safety data sheet, and thymosin beta-4 fragment (1-4), the name on this listing, says where the sequence sits in the larger protein. The safety data sheet gives CAS 127103-11-1 and the formula C20H33N5O9. Lenfant and colleagues established the structure in 1989 from peptide purified out of fetal calf bone marrow, using amino acid analysis, fast atom bombardment mass spectrometry and proton NMR, and confirmed it against a synthetic copy; they gave a relative molecular mass of 4871.
The exact structure matters for activity. Robinson and colleagues found that Ac-SDKP does not inhibit stem cells directly but blocks a proliferation stimulator found in regenerating blood-forming tissue, and that analogues with an extra aspartate or a beta-linked aspartate lost that blocking effect, while the tripeptide SDK kept it2. How the identity and purity of a peptide are measured is covered in peptide purity testing.
What is in each capsule
Each hard gelatin capsule contains 500 mcg of Ac-SDKP blended with microcrystalline cellulose as a filler, and each bottle holds 60 capsules. The safety data sheet classifies none of the three ingredients (peptide, cellulose and gelatin) as hazardous. There is nothing to reconstitute. Keep the bottle tightly closed at room temperature, 15 to 25 °C, dry and protected from light, and keep it labelled and out of reach of unauthorised people. General guidance on keeping peptides is in peptide storage and stability.
What the research covers
A regulator of blood-forming stem cells
Ac-SDKP was first identified as an inhibitor of haematopoietic stem cell proliferation. Lenfant and colleagues purified it from fetal calf bone marrow and showed that both the natural and the synthetic peptide stopped spleen colony-forming units in mice from being recruited into DNA synthesis after the animals had received the cytotoxic drug cytosine arabinonucleoside1.
Where it comes from and how it is cleared
Ac-SDKP is found throughout the body and is hydrolysed almost exclusively by angiotensin-converting enzyme (ACE)3. Rousseau and colleagues showed that both active sites of human ACE cleave it, but the N-terminal site does so about 50 times faster, making Ac-SDKP the first highly specific substrate known for that site; they suggested that ACE may control its local concentration in the body4. Its likely source is thymosin beta-4. Cavasin and colleagues found that kidney cortex homogenates produced Ac-SDKP from added thymosin beta-4 unless prolyl oligopeptidase was inhibited, and that long-term inhibition of that enzyme in rats lowered Ac-SDKP in plasma, heart and kidney3. The same paper notes that long-term Ac-SDKP treatment reduced cardiac and renal fibrosis and inflammatory cell infiltration in hypertensive rats3.
What is not established
All of this work was done in tissue homogenates, isolated enzymes, mice and rats. None of these studies used an oral form, so they say nothing about what happens to Ac-SDKP in a capsule or in the gut. No human data appear in the references.
Frequently asked questions
Is Ac-SDKP the same as TB-500?
No. TB-500 here is full-length thymosin beta-4, a 43-residue protein. Ac-SDKP is only its first four residues, acetylated, with a relative molecular mass of 487. An enzyme can release Ac-SDKP from thymosin beta-4, but they are different molecules with separate research literatures.
Why does the compound have several names?
Goralatide, Ac-SDKP and thymosin beta-4 fragment (1-4) all describe the same tetrapeptide. Ac-SDKP spells out the acetylated sequence Ser-Asp-Lys-Pro, the fragment name gives its position at the start of thymosin beta-4, and goralatide is the name on the safety data sheet. CAS 127103-11-1 covers all of them.
How should the capsules be stored?
Keep the bottle tightly closed at room temperature, between 15 and 25 °C, dry and away from light, as the safety data sheet specifies. Capsules are not reconstituted, so the frozen and refrigerated storage used for freeze-dried peptide vials does not apply here.
References
- Lenfant M, Wdzieczak-Bakala J, Guittet E, et al. Inhibitor of hematopoietic pluripotent stem cell proliferation: purification and determination of its structure. Proc Natl Acad Sci U S A. 1989;86(3):779-82. DOI · PubMed
- Robinson S, Lenfant M, Wdzieczak-Bakala J, et al. The molecular specificity of action of the tetrapeptide acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) in the control of hematopoietic stem cell proliferation. Stem Cells. 1993;11(5):422-7. DOI · PubMed
- Cavasin MA, Rhaleb NE, Yang XP, et al. Prolyl oligopeptidase is involved in release of the antifibrotic peptide Ac-SDKP. Hypertension. 2004;43(5):1140-5. DOI · PubMed
- Rousseau A, Michaud A, Chauvet MT, et al. The hemoregulatory peptide N-acetyl-Ser-Asp-Lys-Pro is a natural and specific substrate of the N-terminal active site of human angiotensin-converting enzyme. J Biol Chem. 1995;270(8):3656-61. DOI · PubMed
For laboratory research use only. Not for human or veterinary consumption. Products have not been evaluated by the U.S. Food and Drug Administration and are not intended to diagnose, treat, cure or prevent any disease.