THE INTERCONVERSION OF SUGARS IN NATURE 



LUIS F. LELOIR, Instituto de Investigaciones Bioquimicas, Fundacion 



Campomar, Buenos Aires 



The amazing variety of carbohydrates manufactured by 

 plants and animals has incited the accomplishment of an equally 

 amazing work by the sugar chemists. This work, which gained 

 impetus with Emil Fischer's intelligent research on the structure 

 of sugars, has not slackened, and we are now confronted with 

 an enormous amount of information on the occurrence of differ- 

 ent carbohydrates in natural products. But the question which 

 was probably in the minds of all these chemists — how does this 

 organism make this particular sugar? — has only recently fallen 

 within the frontiers of research. 



It is fortunate for the biochemist that nature does not seem 

 to have "discovered" all the possible isomers of sugars. Thus, 

 of the sixteen possible aldohexoses, only four or five occur 

 naturally. The problem, therefore, becomes more limited, but 

 by no means small, since, including the aldoses, ketoses, amino 

 and deoxy sugars, and uronic acids, the number of monosac- 

 charides known to occur in nature is well over twenty. These 

 substances are distributed in the most varied types of organisms. 

 The biochemist may have to deal with molds or lobsters in order 

 to study glucosamine derivatives, or with umbilical cords or 



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