The peptidoglycan in walls of Butyribacterium rettgeri

The wall peptidoglycan in Butyribacterium rettgeri is composed of Nα-(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 є-amino group or D-ornithine through its δ-amino group, to the carboxyl group of the C-terminal D-alanine residue of another peptide subunit. D-Lysine and D-ornithine bridges occur in the ratio of 2:1.
The Streptomyces KM endopeptidase hydrolyses the Nα-( D-alanyl)-D-lysine and Nα-(D-alanyl)-D-ornithine 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.