Diprotin A (Synonyms: Ile-Pro-Ile)

Diprotin A is a tripeptide inhibitor of dipeptidyl peptidase 4 (DPP-4; IC50 = 1.1 μg/ml).1 It inhibits degradation of glucagon-like peptide 1 in culture with insulin-secreting BRIN-BD11 rat pancreatic β-cells when used at a concentration of 25 μM.2 Diprotin A (5 mg/ml) pre-incubation enhances chemotaxis of murine embryonic stem cells towards stromal cell-derived factor-1 (SDF-1/CXCL12) in vitro.3 Pre-incubation of CD34+ human umbilical cord blood cells with diprotin A (5 mM) prior to injection increases engraftment in NOD/SCID recipient mice.4

References
1. Umezawa, H., Aoyagi, T., Ogawa, K., et al. Diprotins A and B, inhibitors of dipeptidyl aminopeptidase IV, produced by bacteria. J. Antibiot. (Tokyo) 37(4), 422-425 (1984).
2. Green, B.D., Liu, H.K., McCluskey, J.T., et al. Function of a long-term, GLP-1-treated, insulin-secreting cell line is improved by preventing DPP IV-mediated degradation of GLP-1. Diabetes Obes. Metab. 7(5), 563-569 (2005).
3. Guo, Y., Hangoc, G., Bian, H., et al. SDF-1/CXCL12 enhances survival and chemotaxis of murine embryonic stem cells and production of primitive and definitive hematopoietic progenitor cells. Stem Cells 23(9), 1324-1332 (2005).
4. Campbell, T.B., Hangoc, G., Liu, Y., et al. Inhibition of CD26 in human cord blood CD34+ cells enhances their engraftment of nonobese diabetic/severe combined immunodeficiency mice. Stem Cells Dev. 16(3), 347-354 (2007).