Isolation of peptide ligands that inhibit glutamate racemase activity froma random phage display library

Several new antibacterial agents are currently being developed in response to the emergence of bacterial resistance to existing antibiotic substances, The new agents include compounds that interfere with bacterial membrane fu nction. The peptidoglycan component of the bacterial cell wall is synthesiz ed by glutamate racemase, and this enzyme is responsible for the biosynthes is of D-glutamate, which is an essential component of cell wall peptidoglyc an. In this study, we screened a phage display library expressing random dodeca peptides on the surface of bacteriophage against an Escherichia coil glutam ate racemase, and isolated specific peptide sequences that bind to the enzy me. Twenty-seven positive phage clones were analyzed, and seven different p eptide sequences were obtained. Among them, the peptide sequence His-Pro-Tr p-His-Lys-Lys-His-Pro-Asp-Arg-Lys-Thr was found most frequently, suggesting that this peptide might have the highest affinity to glutamate racemase, T he positive phage clones and HPWHKKHPDRKT synthetic peptide were able to in hibit glutamate racemase activity in vitro, implying that our peptide inhib itors may be utilized for the molecular design of new potential antibacteri al agents targeting cell wall synthesis.