Discovery of a Non-β-Lactam Inhibitor of Escherichia Coli L, Dcarboxypeptidase A Using a Coupled Fluorescent Assay

During peptidoglycan recycling in Escherichia coli, L, D-carboxypeptidase A cleaves the tetrapeptide L-Ala-γ-D-Glu-meso-diaminopimelic acid-D-Ala, producing tripeptide and D-Ala. Previous studies utilized substrate purified from bacteria, with HPLC detection of tripeptide. Herein, synthetic peptide substrate containing L-Lys in place of diaminopimelic acid, and a fluorescent assay for D-Ala, were used to identify a benzoxazine as a non-β-lactam inhibitor of the enzyme.