CARBOHYDRATES 51 



Trehalose may be hydrolyzed into glucose by dilute acids 

 and by the enzyme " trehalase," which is contained in many 

 yeasts and in several species of fungi. It is strongly dextro- 

 rotatory (specific rotatory power, +199). It is not fermentable 

 by yeast. 



Trehalose appears to replace sucrose in those plants which con- 

 tain no chlorophyll and do not elaborate starch. The quantity of 

 trehalose in such plants reaches a maximum just before spore- 

 formation begins. Since it is manufactured in the absence of 

 chlorophyll, its formation must be accomplished by some other 

 means than photosynthesis, yet it is composed wholly of glucose 

 a natural photosynthetic product. 



Maltose rarely occurs as such in plants, although its presence 

 in the cell-sap of leaves has sometimes been reported. It is pro- 

 duced in large quantities by the hydrolysis of starch during the 

 germination of barley and other grains. This hydrolysis is brought 

 about by the enzyme " diastase," which is present in the sprouting 

 grain. 



Maltose is easily soluble in water, and crystallizes in masses of 

 slender needles. It is a reducing sugar; readily forms a charac- 

 teristic osazone; is strongly dextrorotatory (specific rotatory 

 power +137); and is readily fermented by ordinary brewer's 

 yeast, which contains both " maltase " (the enzyme which hydro- 

 lyzes maltose to glucose) and " zymase " (the alcohol-producing 

 enzyme). When hydrolyzed, either by dilute acids or by maltase, 

 one molecule of maltose yields two molecules of glucose. Its com- 

 ponent hexoses are, therefore, the same as those of trehalose, a 

 non-reducing sugar, this difference in properties being due to the 

 difference in the point of linkage between the two glucose molecules, 

 that for maltose being such as to leave one of the aldehyde groups 

 potentially active, as shown in the following formula, 



-0 : 



CH 2 OH CHOH CH CHOH CHOH CH 



CHOH CHOH CHOH CH CHOH CH 2 



L J 



