62 



MICROBIAL CELL WALLS 



and Streptomyces F^ enzyme yielded disaccharide from the 

 tetrasaccharide, although the activity of the latter enzyme 

 was much weaker than that of lysozyme.^^ The two en- 

 zymes, moreover, are capable of degrading mono- and di- 

 chitibiose (i.e. the di- and tetrasaccharides of N-acetyl- 

 glucosamine), thus clearly showing that they possess 

 /?(!—> 4) N-acetylglucosaminidase activity.^--" This also 

 confirmed the earlier conclusion by Berger and Weiser ^^ 

 that the limited action of lysozyme on purified chitin indi- 

 cated its /5-glucosaminidase properties. The experimental 

 evidence is therefore in accordance with the structure of the 

 tetrasaccharide being a f3{l — > 4) dimer of the disaccharide, 

 as shown in Fig. 13. 



Independent confirmation that the disaccharide is the 

 simplest product of lysozyme action on its substrate in the 

 cell-wall mucopeptide of Micrococcus lysodeikticus has 

 come from the investigations of Perkins,-*' ^^ and the struc- 

 ture suggested is identical to that proposed by Salton and 

 Ghuysen.^- A disaccharide of N-acetylglucosamine and 

 N-acetylmuramic acid has also been detected in partial acid 

 hydrolysates of walls of Micrococcus lysodeikticus.-'^'-^ 



The nature of the fragments obtained on digestion of 

 walls with lysozyme has provided us with an idea of the 

 structure of the cell-wall mucopeptide. Thus the wall 



CH^CHCOOH 



CH2OH 



H HO/^ r H H >— — 0' 

 H NHCOCH3 O' H NHCOCH3 CH2OH 

 CH3CHCOOH 



CKr 



Fig. 13. Proposed structure of the tetrasaccharide enzymically released 

 from Micrococcus lysodeikticus walls.12, 23 



