AMINO SUGARS '21 



phosphor, lase (224). Presumably, other environmental factors are 

 influential; on a priori grounds it is to be expected that the con- 

 centration of available carbohydrate and the carbon: nitrogen ratio of 

 the medium are important. Oxygen is required for the synthesis of 

 polysaccharide by Aspergillus niger (2< 



The function of fungal poh saccharides is almost certainly as a 

 reserve food., and the data of Ergle (70 on glycogen utilization dur: . 

 the germination of sclerotia bear out this contention. This view of 

 polysaccharides as one form in which fungi can store energy was first 

 clearly stated by Chrzaszcz and Tiukow '/y in opposition to an earlier 

 view of polysaccharide formation as a symptom of a deranged metabo- 

 lism. It should be noted that under some cultural conditions the 

 polysaccharide formed may never in fact be utilized., cell death and 

 autolysis intervening before the carbohydrate supply becomes limiting 

 and before the reserves are attacked. 



Several fungi pathogenic to man form polysaccharides, often as- 

 sociated with a capsule and often immunologically active. Those of 

 Coccidioides immitis and Cryptococcus 'Torulor./ spp. are listed in 

 Chapter 2: others are reviewed by Xickerson 158). 



5. THE METABOLISM OF AMINO SUGARS 



The only amino sugar which has been studied extensively is r> 

 glucosamine | 2-amino-D-glucose), interest in which arises primarily 

 from the fact that its N-acetyl derivative is the basic unit of chitin, the 

 cell wall material of most fungi Chapter 2). 



Conceivably, the conversion of glucose to glucosamine could proceed 

 with glucosone. CfTOH— CHOH — CO— CHO ; as intermediate and 

 glucosone is formed by Aspergillus parasiticus, at least under some 

 conditions 29 . However, in Xeurospora crassa extracts glucosamine 

 is formed by transamidation from glutamine (126) as folio- 



Hexose-6-phosphate — glutamine -^ glucosamine-6-phosphate — 



glutamic acid (9) 



It appears from other work that the hexose phosphate involved directly 

 in the reaction is fructose-6-phosphate 26). 



Glucosamine appears in chitin and in animal mucopolysaccharides 

 as the N-acetyl derivative. Introduction of the acetyl group involves 

 aceu 1-coenzvme A in both animals and Xeurospora crassa (52, 12 

 in N. crassa it is not certain whether free glucosamine or its phosphate 

 is the compound acetylated. 



Amino sugars are frequently found as constituents of antibiotics. 



