Overview

TB-500 peptide, also known as thymosin β(4), includes a distinct peptide segment (17)LKKTETQ(23), which acts as the active site and which researchers consider potentially impactful in actin binding, cell migration, and wound healing.⁽²⁾ The amino acid sequence of TB-500 is:
Ac-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-OH.

Actins are essential proteins that form a key component of the cytoskeleton within cells, serving not only to maintain cellular structure but also to facilitate various cellular functions, including movement. Actin is suggested to be critical in supporting these cellular structures and processes. Thymosin beta-4 and, thus, TB-500 are believed to interact with actin, potentially by binding to globular actin (G-actin), a precursor to filamentous actin (F-actin). This interaction is thought to hinder the transformation of G-actin into F-actin, a process known as actin sequestration, and is likely to increase the availability of G-actin. The inhibition of F-actin formation by thymosin beta-4 may conceivably modify the structure of the cellular cytoskeleton, impacting cellular abilities for movement and morphological changes. Such changes are tentatively linked to various physiological and pathological states where cell motility is essential, including wound healing, tissue regeneration, and the progression of cancer through metastasis.⁽³⁾

Furthermore, Thymosin beta-4 has been detected not only within cells but also extracellularly, such as in blood plasma and wound exudates. Preliminary studies involving vascular cells suggest that Thymosin beta-4 is extracellular, it might influence cellular functions like motility and the formation of new blood vessels (angiogenesis).^(11,12) It is postulated that Thymosin beta-4 might exert this potential through its interactions with ATP synthase enzymes located on the cell surface, which are critical for cellular energy production. These findings indicate a broader scope of action for thymosin beta-4, impacting both intra- and extracellular processes.