ENZYMIC DEGRADATION AND BIOSYNTHESIS 63 



Backbone structure 



(1-^6) (1-^4) (1-^6) (1^4) (1^6) (1-^4) (1^6) 

 AG AMA AG AMA AG AMA AG AMA- 



Peptide Lysozyme Peptide 



Sensitive bonds 



Fig. 14. Backbone structure proposed for Micrococcus lysodeikticus 

 wall.23 



probably possesses a backbone structure of alternating 

 groups of N-acetylmuramic acid and N-acetylglucosamine 

 with alternating ^(1^4) and /?(1 ^ 6) linkages. Some 

 of the muramic acid residues would have peptide substitu- 

 ents, and the possible structure of the wall and the distribu- 

 tion of lysozyme sensitive bonds is shown in Fig. 14. 



The isolation of a small molecular weight mucopeptide 

 in the dialyzable fraction of lysozyme-digested walls of Mi- 

 crococcus lysodeikticus ^^ has clearly shown that lysozyme 

 can degrade the backbone down to a disaccharide residue 

 possessing a peptide linked through muramic acid, as in the 

 structure in Fig. 15, which shows in addition the linkage 

 sensitive to the Streptomyces amidase.^^ 



Although it is now possible to understand the manner in 

 which lysozyme degrades the bacterial walls, yielding a 

 variety of products, some containing all of the parent amino 

 acids and amino sugars in the same molar proportions as in 

 the intact cell wall (e.g. the diffusible mucopeptide) as well 

 as the di- and tetrasaccharides, many of the general prob- 

 lems of understanding lysozyme sensitivity remain to be 

 solved. O-acetyl substituents have been shown to be im- 

 portant in governing this sensitivity in mutant strains of 



