[en] In a major part of the wall peptidoglycans of Streptomyces sp. and of Clostridium perfringens, L-alanyl-D-isoglutaminyl-(L1)-LL-diaminopimelyl-(L1)-D-alanine peptides are cross-linked via D-alanylglycyl-(L2)-LL-diaminopimelic acid linkages (peptidoglycan of the chemotype II group). The Myxobacter AL-I endopeptidase hydrolyzes both D-alanyl-glycine and glycyl-LL-diaminopimelic acid linkages in the walls of C. perfringens, liberating free glycine. In contrast, the Myxobacter AL-I endopeptidase hydrolyzes only D-alanyl-glycine linkages in walls of Streptomyces sp. and the liberation of the glycine residues requires subsequent treatment with an aminopeptidase. No explanation for this observation can be proposed at this time. A minor component of the AL-I endopeptidase hydrolysate of the Streptomyces and C. perfringens walls is a resistant peptide dimer. Analyses indicate that the cross-link in this dimer may be mediated through LL-diamino-pimelylglycyl-LL-diaminopimelic acid linkages.
The C termini of the peptide moieties in the wall peptidoglycans are either D-alanine or LL-diarninopimelic acid but never D-alanyl-D-alanine, thus indicating the presence in these microorganisms of carboxypeptidases similar to those of Escherichia coli.