20 ENZYME ACTION [ch. 



According to the substances upon which they act (the substrates) 

 they may be further sub-classified as follows : 



(1) Fat-splitting enzymes, which hydrolyze fats into fatty acids 

 and glycerol : lipase. 



(2) Carbohydrate-splitting enzymes : 



Diastase, which hydrolyzes starch into dextrin and maltose. 



Invertase, which hydrolyzes cane-sugar into dextrose and laevulose. 



Maltase, which hydrolyzes maltose into dextrose. 



Inulase, which hydrolyzes inulin into laevulose. 



Cytase, which hydrolyzes hemicellulose into mannose and galactose. 



Pectinase, which hydrolyzes pectic compounds into arabinose. 



(3) Glucoside-splitting enzymes : 



Emulsin, which hydrolyzes amygdalin into benzaldehyde, prussic 

 acid and glucose. 



Myrosin, which hydrolyzes sinigrin into allylisothiocyanate, potassium 

 hydrogen sulphate and glucose. 



(4) Protein-splitting enzymes (proteases) : 



Pepsin-like enzymes, which hydrolyze proteins into albumoses and 

 peptones. 



Erepsin-like enzymes, which hydrolyze peptones into polypeptides 

 and amino-acids. 



B. Oxidizing enzymes : 



Peroxidases, which decompose peroxides and set fi-ee oxygen in 

 the active state, probably as atomic oxygen. 



Catalases, which decompose hydrogen peroxide and set fi-ee oxygen 

 in the molecular condition. 



C. Fermenting enzymes: Zymase of yeast and also of higher plants, 

 which brings about the decomposition of certain hexoses, such as glucose, 

 with the formation of alcohol and carbon dioxide. Probably a series of 

 reactions including oxidation, reduction and hydrolysis are involved. 



D. Coagulating enzymes : Pectase, which coagulates soluble pectic 

 compounds. 



E. Reducing enzymes : Reductase. The precise function of these 

 enzymes is unknown. 



Most of these various classes of enzymes will be dealt with in detail 

 in connexion with the chemical substances on which they react. 



An excellent demonstration of the fiict that a single cell may contain 

 all the various enzymes connected with the processes of metabolism is 



