Isolation procedure and properties of monomer unit from lysozyme digest of peptidoglycan complex excreted into the medium by penicillin-treated Brevibacterium divaricatum mutant.

1. The peptidoglycan complex excreted in large amounts into the medium by the biotin-requiring mutant Brevibacterium divaricatum NRRL-2311 incubated in the presence of penicillin for 1 h has been investigated. A convenient isolation procedure with high yield for the pure monomeric unit from lysozyme digest of the accumulated polymer is described. 2. It is shown that the released peptidoglycan possesses the linear uncross-linked structure made of repeating disaccharide-pentapeptide unit [GlcNAc-MurNac-Ala-D-Glyn(meso-DAP-D-Ala-D-Ala)] which was isolated by stepwise gel filtration and fractionation of the digestion mixture in 10-mg quantities. Evidence that the minor digestion product of accumulated peptidoglycan possesses the glycan-linked dimer structure is given. Under conditions of beta-elimination, the monomeric unit yielded a lactylpentapeptide which was isolated in pure form by gel filtration. 3. The monomer unit originating from the cultures to which L-[U-14C]glutamic acid was added simultaneously with penicillin incorporated the label exclusively in the peptide chain, whereas that labeled from E11-14C]acetate as the precursor contained radioactivity in both the peptide chain (53%) and N-acetylamino groups (47%) of the glycan portion.