OCCURRENCE OF HYDROLYTIC PLANT ENZYMES 469 



abundant in green leaves and actively growing plant parts. It is so named 

 because it is the form of diastase which hydrolyzes the starch in leaves be- 

 fore it is translocated to other parts of the plant. 



Maltose is the enzyme which catalyzes the digestion of maltose to glucose 

 according to the following equation : 



„ Maltase ^ -r-, ^ 



C12H22O11 + H2O > 1 CeHiaOe 



Maltose Glucose 



Maltase is one of the most widely distributed of the plant carbohydrases and 

 is almost invariably found to be present in tissues which contain amylase. 

 It is also produced by many species of micro-organisms and is found in various 

 organs of the higher animals. This enzyme can also hydrolyze a-glycosides. 

 Maltose itself is an a-glycoside of glucose with glucose. 



Sucrase {invertase) catalyzes the hydrolysis ("inversion") of sucrose to 

 hexose sugars according to the well known equation : 



C12H22O11 + H2O -^ C6H12O6 + C6H12O6 



Sucrose Glucose Fructose 



This is another enzyme of widespread occurrence throughout the plant and 

 animal kingdoms. It has been found in practically all of the green plants 

 which have been examined for its presence, occurs in the bodies of the higher 

 animals, and is produced by many micro-organisms. Sucrase is synthesized in 

 great abundance by many of the yeasts, hence these organisms are generally 

 used as a source of this enzyme. 



Since the hydrolysis of sucrose is a relatively simple reaction, involving 

 well-known products, and can be followed very simply by means of a polar- 

 imeter (Chap. XXII), it has been studied more comprehensively than any 

 other process catalyzed by enzymes. Most of the studies of the effect of 

 various factors upon the velocity of enzyme reactions have been made with 

 this enzyme. Its only rival as a favorite in such studies is catalase (Chap. 

 XXX). 



Inulase is the enzyme which catalyzes the hydrolysis of inulin to fruc- 

 tose, according to the equation : 



(CoHio05)n + n H2O ^""'"' > n CgHi206 



Inulin Fructose 



This enzyme appears to be of rather limited occurrence. It has been found 

 in the tubers of the Jerusalem artichoke {Helianthus tuberosus) and in 

 several other species which accumulate inulin. It is also produced by certain 

 fungi {Aspergillus niger and Penicilliuiii glaucuin), and in some animals, 

 especially of the invertebrate group. 



