ENZYMIC DEGRADATION AND BIOSYNTHESIS 65 



penicillin-treated Staphylococcus aureus by Park and John- 

 son -^ and Park -^ and the subsequent recognition of the 

 biochemical significance of these compounds by Park and 

 Strominger ^o stimulated a great deal of interest in the mode 

 of action of penicillin and the mechanism of biosynthesis 

 of bacterial cell walls. Much of the work on wall biosyn- 

 thesis has thus been confined to recognizing wall inter- 

 mediates accumulating in the presence of various antibiotic 

 inhibitors and has been performed mainly with bacterial 

 cells. 



Yeasts and Fungi. So far as I am aware, there have been 

 no direct studies of the biosynthesis of walls of yeasts or 

 fungi. However, it is well known that possible intermedi- 

 ates in the form of nucleotide anhydrides occur in yeasts. 

 Uridine diphospho-(UDP)-glucose,3i UDP-acetylglucosa- 

 mine,^- and guanosine diphospho-(GDP)-mannose ^^ could 

 all be regarded as potential wall intermediates, since the 

 monosaccharide moieties of all three nucleotides occur in 

 the walls of yeasts. Although there have been no direct 

 observations involving a transfer of the sugar moieties of 

 these nucleotides into wall compounds, it is conceivable 

 that they may well follow the known transglycosylation re- 

 actions ^^-^^ established for uridine nucleotides and follow- 

 ing the general type of reaction given below: 



UDP-X + ROH — UDP -f RO-X 



Glaser and Brown ^e have investigated the biosynthesis 

 of chitin by extracts of Neurospora crassa, which is known 

 to contain poly-N-acetylglucosamine in the mycelia.^^ En- 

 zyme preparations catalyzed the synthesis of chitin by the 

 following reaction: 



UDP-acetylglucosamine + (chitodextrin)^ 



^ UDP + (chitodextrin)„+i 



