The Peptidoglycan in Walls of Butyribacterium rettgeri

The wall peptidoglycan in Butyribacterium rettgeri is composed of N^α-(L-seryl-γ-D-glutamyl)-L-ornithyl-D-alanine subunits. The peptide subunits are cross-linked by means of a D-lysine or a D-ornithine residue, extending from the α-carboxyl group of the glutamic acid of one peptide subunit, to which D-lysine is linked through its ε-amino group or D-omithine through its δ-amino group, to the carboxyl group of the Cterminal D-alanine residue of another peptide subunit. D-Lysine and D-omithine bridges occur in the ratio of 2:1. The Streptomyces KM endopeptidase hydrolyses the N^α-(D-alanyl)-D-lysine and N^α-(D-alanyl)-D-omithine linkages and causes wall solubilization. The walls, as they are prepared, have a low degree of cross-linking. About 59% of the peptide subunits occur as monomers (18%), dimers (24%), and trimers (17%). Higher oligomers account for the remaining 41 %. The disaccharide units obtained after sequential treatment with Streptomyces F₁ endo-N-acetylmuramidase and Streptomyces N-acetylmuramyl-L-alanine amidase are all β-1,4-N-acetylglucosaminyl-N-acetylmuramic acid.