Précisions sur la structure des complexes disaccharide-peptide libérés des parois de Micrococcus lysodeikticus sous l'action des β (I → 4) N-acetylhexosaminidases

Two types of disaccaride-peptide complexes have been studied. In a first type of complex, the fragment 6-O-[beta]-N-acetylglucosaminyl-N-acetyl-muraminyl is joined to a peptide moiety consisting of 2 alanines, 1 glycine, 1 glutamic acid and 1 lysine, by an amide bond between the COOH of N-acetylmuramic acid and the NH2 of one of the alanine residues of the peptide. The reaction with 1-fluoro-2,4 dinitrobenzene shows that the [epsilon]-NH2 group of lysine is free. The electroheophoretic properties suggest that the [gamma]-COOH group of glutamic acid and an unspecified [alpha]-COOH group are free too. The second type of complex is a dimer of the former, joined by a peptide linkage between an [epsilon]-NH2 group of lysine and, very probably, an [alpha]-COOH group. THe F2B amidase splits the amidic acetylmuraminyl-alanine linkage. Consequently, the disaccharide is liberated and a new free [alpha]-NH2 group of alanine appears in the peptide moiety.