STRUCTURE OF CELL WALL OF STAPHYLOCOCCUS AUREUS STRAIN COPENHAGEN .7. MODE OF ACTION OF BACTERIOLYTIC PEPTIDASE FROM MYXOBACTER AND ISOLATION OF INTACT CELL WALL POLYSACCHARIDES

The mode of action of the lytic peptidase isolated from culture filtrates of Myxobacterium strain AL-1 has been studied by kinetic analysis of end groups liberated during hydrolysis and by fractionation and analysis of the products of its action on isolated cell walls of S. aureus and Arthrobacter crystallopoietes. The Myxobacter enzyme solubilizes these walls by a primary attack on their peptide cross-bridges (pentaglycine in the case of S. aureus and L-alanine in the case of A. crystallopoietes) which interlink peptidoglycan strands. These bridges are attacked at their linkage to the D-alanyl terminus of the basal tetrapeptide (L-Ala-y-D-Glu(ff-CONHo)-L-Lys-D-Ala) which is found in both of these peptidoglycans. Hydrolysis of the N-acetylmuramyl-L-alanine linkages between the polysaccharide and the peptides occurs at a slower rate in both cases, with eventual liberation of small peptide fragments, undegraded polysaccharide, and a polysaccharide-teichoic acid complex. The periodate insensitivity and chemical analyses of the polysaccharides are consistent with the structure of alternating [beta]-1,4-linked residues of N-acetylglucosamine and N-acetylmuramic acid, predicted from previous analyses of disaccharides isolated from the S. aureus polysaccharide. Analyses show the polysaccharides to be polydisperse with average chain lengths of 19-25 hexosamine residues but containing molecules as short as 12 and as long as 70-100 residues. The polysaccharide is relatively insensitive to egg white lysozyme and other endo-N-acetylmuramidases, but it is rapidly attacked by an endo-N-acetylglucosaminidase.