THE CHEMISTRY OF DIGESTION 



989 



(a) Proteolytic or protein-splitting enzymes, such as pepsin, give rise to a 

 hydrolytic cleavage of the protein molecule. 



(6) Lipolytic or fat-splitting enzymes, such as steapsin, cause a hydrolytic 

 cleavage of the fat molecule. 



(c) Amylolytic or starch-splitting enzymes, such as ptyalin, produce a hydro- 

 lytic cleavage of the starch molecule. 



(d) Inverting enzymes, such as maltase, split the disaccharides into monosac- 

 charides and the latter into simpler molecules. 



(e) Oxidizing enzymes, such as the oxidases of the tissues, which aid in internal 

 respiration. 



(/) Coagulating enzymes, such as rennin, which change soluble into insoluble 

 proteins. 



(g) Diaminizing enzymes, such as alanin, which split off an NH 2 group from an 

 amino-acid as ammonia. 



In the following table are included some of the ferments with which 

 we are chiefly concerned at the present time, it being the custom 

 to designate them by the name of the substance upon which they act 

 and to affix the letters, ase. This suggestion (Duclaux) has been fol- 

 lowed in most instances, the only exceptions being those enzymes which 

 have been recognized for a long time, such as ptyalin, pepsin and trypsin. 



Character of action 

 Starch maltose 

 Starch maltose 

 Glycogen dextrose 

 Cane-sugar dextrose 

 Maltose dextrose 

 Lactose dextrose and galactose 



Glucose lactic acid 



Neutral fats fatty acids and 



glycerin 

 Neutral fats fatty acids and 



glycerin 

 Proteins peptones and amino- 



acids 

 Proteins peptones and amino- 



acids 



Proteoses amino-acids 

 Nucleic acid purin bases 

 Trypsinogen trypsin 

 Guanin xanthin 

 Adenin hypoxanthin 



A m i n o-acids oxyacids 



arginin urea 



Oxidizes organic substances 

 Decomposes hydrogen peroxide 

 Causes deoxidation 



Proteolytic 



Deaminizing 



Erepsin 



Nuclease 



Enterokinase 

 f Guanase 

 I Adenase 

 i Deaminase 

 1 Arginase 



Oxidase 

 Catalase 

 Reductase 



Small intestine 



Pancreas, spleen, thymus, etc. 



Small intestine 



Thymus, adrenals and pancreas 



Spleen, pancreas and liver 



Tissues 



Liver and spleen 



Lungs, liver and tissues 



Tissues 



Tissues 



Although still incomplete, this enumeration proves very clearly 

 that almost every reaction necessitates the presence of a particular 

 enzyme. There can be only one reason for this, namely, that they are 

 specific in their action and cannot be employed interchangingly to 

 produce one and the same result. Thus, ptyalin changes starch into 

 maltose, but does not affect the fats and proteins, nor even the other 

 carbohydrates. Quite similarly, given a number of closely allied 



