MONOS^^f. 



66 CARBOHYDRATES MONOSAlTTIARIDES 



great importance in the light of the fact that the decomposition of 

 glucose, or glycogen which is an anhydride of glucose, in muscular 

 tissue leads to the formation of lactic acid. 



The action of alkalies upon glucose led to the suspicion that if am- 

 monia were employed amino-derivatives of hydroxy-acids, such as are 

 found among the constituent radicals of the proteins, might possibly 

 be formed, and it was found by Windaus and Knoop that, as a matter 

 of fact, ammonia, acting upon glucose, mannosiMJtalose, sorbose, 

 arabinose, xylose, rhamnose or lactose yields Methyl^^oxaline : 



CH 3 C NH 



>CH 



HC N/ 



No other amino-products of this decomposition were identified, but 

 this one is of extraordinary interest, because of the very great impor- 

 tance and variety of roles played by the Iminazole ring in physiological 



phenomena. While it is very doubtful whether the synthesis of this 

 ring is possible for animal tissues to accomplish, and in fact there is 

 much evidence tending to show that it is not, yet it is, of course, unques- 

 tionably accomplished by vegetable tissues, since the iminazole ring 

 in the form of the amino-acid Histidine and in the purine-base moiety 

 of the Nucleic Acids, is an invariable and essential constituent of living 

 matter. 



On heating hexoses in concentrated solution with amino-acids (glyco- 

 coll, alanine, leucine, tyrosine or glutamic acid) the mixture darkens 

 with the formation of "Humin Substances" which are very deeply 

 colored. At the same time carbon dioxide is discharged from the 

 mixture. It is believed that the carbon dioxide is released from the 

 carboxyl-group of the amino-acid which unites with the aldehyde- 

 group of the sugar to form cyclic compounds. Similar substances are 

 formed (from tryptophane) when proteins are hydrolyzed by strong 

 acids in the presence of carbohydrates. 



Certain Derivatives of Glucose. Two derivatives of glucose, 

 Glucuronic Acid and Glucosamin, claim our attention at this juncture, 

 because they are both of profound physiological importance. 



We have seen that on oxidation, glucose yields, first two monobasic 

 acids and thereafter, on continued oxidation, each of these monobasic 

 acids yields the same dibasic acid. One of the monobasic acids is 

 glucuronic acid, the dibasic acid is saccharic acid. The connection 

 between glucose, glucuronic acid and saccharic acid can be seen at a 

 glance from their formulae: 



