L-Val-L-Tyr (valyltyrosine) is amphoteric dipeptide comprising valine and serine. L-Val-L-Tyr is ubiquitous in Nature as one of ~400 possible dipeptides from the incomplete catabolism of proteins. While many dipeptides have demonstrated potent biological activity L-Val-L-Tyr has not been extensively investigated. L-Val-L-Tyr is the precursor of the cyclic diketopiperazine formed by head to tail ring closure and these metabolites play an important role in quorum sensing.