Bacterial-Cell-Wall Peptidoglycan Fragments Produced by Phage lamba or Vi II Endolysin and Containing 1,6-Anhydro-N-acetylmuramic Acid

Abstract

The cell wall peptidoglycan of Escherichia coli or Salmonella typhi were hydrolysed to dialysable non-reducing fragments by partially purified preparations of the bacteriolytic activity present in lysates of phage λ or Vi II. The structure of the two main fragments resulting from this digestion was determined In each case the lack of reducing power is explained by the presence of a 1,6-anhydro-N-acetylmuramic acid residure at what should normally be the reducing end of the peptidoglycan fragment. Furthermore, no d-alanyl-(d)-meso-diaminopimelyl peptide crosslinkages were detected in these fragments. These results indicate that the partially purified preparations of phage λ or phage Vi II endolysin contain at least two different types of hydrolytic activities: a phage endopeptidase responsible for the cleavage of the peptide crosslinkages present in peptidoglycan and a new type of N-acetylmuramidase activity which not only cleaves β-1 → 4 linkages between N-acetylmuramic acid and N-acetylglucosamine residues in the glycan moiety of peptidoglycan, but also catalyses a dehydration with the formation of 1, 6-anhydro-N-acetylmuramic acid residues.