Antibiotic resistance to the beta lactam family of antibiotics, which includes penicillin, is often conferred to bacteria by serine beta lactamases which can break down the inhibitor to harmless products. They are believed to have evolved from D amino peptidases, which hydrolyse the peptide bond between two D amino acids after the N terminal residue. DAP from Othrobacrum anthropi is one such peptidase, and is inhibited by beta lactams. Study of this protein will thus reveal details of how the antibiotic resistance conferring peptidases work. It is found to show significant active site homology with other penicillin binding proteins, including the serine beta lactamases, but very low sequence identity with either group, suggesting that it is part of a novel family which may have given rise to the resistance-conferring enzymes.