76 CARBOHYDRATES AND THEIR [ch. 



used and not chloroform. Finally, if the enzyme is to be extracted from 

 dried material, this must not be heated at too high a temperature 

 previous to the extraction. 



Maltase occurs in quantity in both germinated and ungerminated 

 seeds of cereals. If, in kilning, malt has not been heated at too high a 

 temperature, the maltase may not be destroyed, and, in such cases, malt 

 extract will contain both diastase and maltase. This would explain the 

 fact that glucose, instead of maltose, has sometimes been obtained by 

 the action of malt diastase on starch. In other cases, when a higher 

 temperature has been employed, the maltase will be destroyed. Maltase 

 itself, of course, does not act directly upon starch but only on maltose. 

 The use of chloroform, as an antiseptic, by some observers explains how 

 they came to overlook the presence of maltase, thus obtaining maltose, 

 and not glucose, as an end product in hydrolysis by malt extracts. The 

 optimum temperature for the maltase reaction is 39'' C. 



The presence of maltase in leaves is not readily shoVvn for the 

 following reasons. Since maltase is destroyed by alcohol, the prepara- 

 tion of a crude precipitate of the enzyme by precipitating a water 

 extract of the leaves is not satisfactory. If the water extract is added 

 directly to maltose, and incubated, hydrolysis may be demonstrated by 

 determining the reducing power of the sugars formed. A control 

 experiment must, however, be made by incubating the water extract 

 alone, and subsequently determining the reducing power of any sugars 

 present. 



Invertase. This enzyme hydrolyzes cane-sugar into one molecule 

 of glucose and one molecule of laevulose : 



CijH...O„ + HoO = C,.,Hi,,Oo + CoHi-.O,,. 

 Invertase is probably very widely distributed in plants. Its presence 

 has been demonstrated in the leaves and stem, though not in the root, 

 of the Beet (Beta vulgaris) (Robertson, Irvine and Dobson, 25). Also in 

 the leaves of a number of other plants (Kastle and Clark, 20). Its de- 

 tection, by its action on sucrose, is not easy on account of the presence 

 of other enzymes and reducing sugars in leaf extracts. 



The absence of invertase from the root of the Beet raises a difficulty 

 as to how the cane-sugar is synthesized from the hexoses supplied from 

 the leaves (see p. 71). Some observers (Robertson, Irvine and Dobson, 

 25) incline to the view that cane-sugar is synthesized in the stems and 

 travels as such to the roots. Others (Davis, Daish and Sawyer, 15) 

 maintain that the cane-sugar is synthesized in the root, even though 

 invertase is absent. 



