242 A TEXT-BOOK OF BOTANY. 



their action, as, for example, emulsin or sinaptase, which decom- 

 poses a number of the glucosides at a temperature of 35° to 40° 

 C, while amylase, the ferment of germinating seeds, requires a 

 somewhat higher temperature, namely, 50° to 70° C. 



Another property of these ferments, which is generally re- 

 garded as characteristic of them, is that of becoming inactive when 

 solutions are heated to a temperature of 100° C. Nothing is 

 known with regard to the composition and constitution of the 

 ferments, and they are usually classified according to the class 

 of substances which they decompose. Thus, amylases act upon 

 starch grains with the formation of sugar; proteinases break 

 down the true proteins, etc. 



The following is an enumeration ot the principal plant 

 enzymes, together with their occurrence and some of their 

 properties : 



Amylase. — The ferment acting upon starch in germinating 

 barley, with the formation of glucose and maltose, was separated 

 by Payen and Persoz in 1833, and called " diastase." This fer- 

 ment occurs, probably, in all parts of all green plants, and is 

 especially abundant in all cells where starch is formed or stored. 

 It is found in large amounts in various cereal grains, and also 

 occurs in the fungi, yeasts, and bacteria. Recent investigation 

 seems to show that in the cells with reserve starches there are two 

 different kinds of diastatic enzymes, the one acting on the soluble 

 starch, called amylase, and the other acting on the insoluble 

 starch or amylopectin, and called amylopectinase. 



Inulinase is the ferment found in the cells of plants contain- 

 ing inulin. It decomposes the latter, changing it into fruit sugar 

 or fructose. Inulinase has no effect upon starch. It has been 

 found in the Compositse and also in Aspergillus, Penicillium, 

 and a number of genera of the Eumycetes. 



Maltase (a-glucosidase) is always associated with the 

 diastases, and from which it has not been separated. It is widely 

 found in the vegetable kingdom, and is especially abundant in 

 malt and some of the yeasts. 



Invertase (a-fructosidase), sometimes also spoken of as in- 

 vertin or sucrose, has the property of converting cane sugar into 

 invert sugar (a mixture of glucose and fructose). It is found in 



