LUIS F. LELOIR 



pig's noses for amino sugars and uronic acids. Or he might use 

 corn cobs which contain xylose, or perhaps algae and microbes 

 which synthesize complicated polysaccharides. The field of 

 sugar interconversions is a field for the lovers of nature and a 

 fascinating chapter of comparative biochemistry. 



Advances in the methodology of enzymes, in analytical pro- 

 cedures, and in the use of tracers have provided us with the 

 means for elucidating many problems of the biogenesis of sugars. 

 Moreover, the first period of enzymology which dealt mostly 

 with catabolic processes has been superseded by the study of 

 synthetic reactions. Following the in vitro synthesis of glycogen, 

 several other polysaccharides have been prepared such as dex- 

 trans and levans, but the synthesis of cellulose, xylans, chitin, 

 has not been accomplished yet, nor has that of mixed polymers 

 such as hyaluronic acid, chondroitin sulfate, gums, and muci- 

 lages. 



As to the disaccharides, trehalose phosphate has been pre- 

 pared enzymically, and sucrose has been synthesized by three 

 different paths. Although biochemists can be justly proud of 

 the progress achieved, our present knowledge of the intercon- 

 version of sugars is limited to several unconnected series of reac- 

 tions which have been found to occur in many organisms, from 

 bacteria to mammals. We may hope that within a few years 

 the picture will be more complete, and that we may know more 

 about the way in which enzymes work inside the cells. This will 

 require the development of delicate methods to replace the 

 present ones, which usually consist in crushing the cells in order 

 to learn their function. 



Organic chemists have developed methods for preparing 

 sugars at will. They can lengthen the chains by cyanohydrin 

 synthesis or with diazomethane. They can shorten them by the 

 Ruff or Wohl degradation. They can oxidize, reduce, epimerize, 

 and invert. Living cells are masters in this technique and can 

 also carry out the most varied reactions. We know that they 

 phosphorylate, oxidize, and shorten the carbon atom chain; 

 transfer two or three carbon atom residues, invert the configura- 



586 



