226 PHARMACEUTICAL BACTERIOLOGY 



At very low temperatures diastase has only a very slight effect upon raw 

 potato starch, while barley and wheat starches are quite actively digested. 



a. Diastases. — These are the true starch splitting ferments and are 

 also called amylases or amylolytic ferments. They are widely distributed 

 in the vegetable and also in the animal kingdom. They are of vital 

 importance to plants and animals. They are the principal ferments in 

 malt, the so-called malt diastase being the best known of all enzymes or 

 ferments. The discovery of malt diastase dates back to 1833, through 

 the investigations of Payen and Persoz, who sought to obtain this enzyme 

 in a pure state by precipitation in alcohol, but in this attempt they were 

 of course not successful. The following are the principal disastatic 

 ferments. 



Amylase. — This is diastase proper and acts on starches, changing them 

 into dextrins and maltose. It is very widely distributed in the vegetable 

 kingdom. The stored starch in plants, which is reserve food, must be 

 transformed into a soluble form before it can enter into circulation through 

 the plant tissues in order that it may finally be assimilated for purposes 

 of plant growth and development and the ferment amylase produces this 

 desired solubility. 



Ptyalin. — This is the starch ferment of the salivary glands, converting 

 starches into maltose. It is a very active ferment, being most energetic 

 in a slightly alkaline medium and is quickly destroyed by acids. Some 

 investigators, declare that very small quantities of hydrochloric acid in- 

 crease the action of ptyalin. However, 0.015 per cent, acid is sufficient to 

 render it inactive. 



Amylopsin. — This is the diastase ferment of the pancreas, closely 

 resembling ptyalin, though it is more active, rapidly liquefying the starch 

 and converting it into dextrin and maltose. It is most active between 30° 

 and 45° C. and is destroyed at 65° C. It is not found alone but in associa- 

 tion with trypsin, steapsin and rennin in the commercial product known as 

 pancreatin. The action of amylopsin is reduced by weak acids, but on the 

 other hand, not appreciably increased in the presence of weak alkalies. 



Liver Diastase. — The glycogenic function of the liver is due to a ferment 

 which (jonverts soluble starch into glycogen and dextrin-like substances. 

 This ferment is also found in the blood, in urine and in tissue cells. 



b. Disaccharide {Diastase) Ferments.- — These ferments act upon biose 

 sugars, converting them into simpler compounds. The principal enzymes 

 of this group are as follows: 



Maltase. — This is very widely distributed in the vegetable kingdom, 

 in different species of Saccharomyces and in other cryptogams. It als'b 

 occurs in the aninjal kingdom. It acts upon maltose, converting it into 

 d-glucose. 



