CHEMISTRY OF CELL WALLS 



39 



now known to contain an amidase capable of acting on 

 small molecular weight mucopeptides (Ghuysen ^^). Thus 

 in the walls of Micrococcus lysodeikticus the number of 

 C-terminal glycine groups could be due to special groupings 

 on the w^all mucopeptide or could represent the true ends 

 of the peptide chains. If the latter, a subunit size of ap- 

 proximately 4000 molecular weight suggests that this wall 

 possesses relatively short peptide chains on the amino sugar 

 backbone.^^ 



Amino Sugar Constituents. The key to understanding 

 the structure of the bacterial cell-wall mucopeptides and 

 mucopolysaccharides was provided by the detection and iso- 

 lation of a new acidic amino sugar by Strange -^ and his 

 colleagues. This amino sugar, now known as muramic 

 acid, was first found in the spore peptides isolated by Strange 



CH 



C.H:;-CH 



CH 



^ CgH^-CH 



O CH, 



L, 



OR 



OMe 

 NH-Ac 



HO>p^ ^ 



NH3+ 



R = — CH 

 \ 



CO^Et .C(0Et)3 



or CH 



CHc 



CH^ 



.COo 



R' = — CH 



CH< 



Fig. 8. Synthesis of muramic acid. 



