Cyclo(L-Pro-L-Val)

Cyclo(L-Pro-L-Val) is a diketopiperazine that has been found in the marine sponge T. ignis, the bacterium B. pumilus, and the fungus A. fumigatus, among others.1,2,3 It is active against the bacteria S. aureus and B. subtilis (MICs = 16.3 and 18.2 μg/ml, respectively) but not E. coli (MIC = >20 μg/ml).3 Cyclo(L-Pro-L-Val) inhibits activation of a LuxR-dependent E. coli biosensor by the quorum-sensing molecule 3-oxo-hexanoyl-homoserine lactone (IC50 = 0.4 mM) and activates violacein pigment production in the LuxR-dependent C. violaceum acyl homoserine lactone reporter strain CV026.4 However, it does not activate or inhibit lacZ-based reporter fusions in S. liquefaciens or A. tumefaciens.

References
1. Schmitz, F.J., Vanderah, D.J., Hollenbeak, K.H., et al. Metabolites from the marine sponge Tedania ignis. A new atisanediol and several known diketopiperazines. J. Org. Chem. 48(22), 3941-3945 (1983).
2. Brack, C., Mikolasch, A., and Schauer, F. 2,5-Diketopiperazines produced by Bacillus pumilus during bacteriolysis of Arthrobacter citreus. Mar. Biotechnol. (NY) 16(4), 385-395 (2014).
3. El-Gendy, B.E.-D.M., and Rateb, M.E. Antibacterial activity of diketopiperazines isolated from a marine fungus using t-butoxycarbonyl group as a simple tool for purification. Bioorg. Med. Chem. Lett. 25(16), 3125-3128 (2015).
4. Holden, M.T.G., Chhabra, S.R., de Nys, R., et al. Quorum-sensing cross talk: Isolation and chemical characterization of cyclic dipeptides from Pseudomonas aeruginosa and other gram-negative bacteria. Mol. Microbiol. 33(6), 1254-1266 (1999).