CHAPTER IX 



THE PROTEINS AND ORGANIC 



CONSTITUENTS OF SALIVA 



PROTEINS 



The proteins of the saliva are complex in origin and nature and 

 are not adequately described by the old classification of mucins 

 and albumins. Further, the electrophoretic classification that has 

 proved useful as a simple description of the plasma proteins helps 

 rather little in the case of saliva. The beginnings of a system of 

 mucoprotein classification based on sugar composition is being 

 worked out by Blix and others but at present is handicapped by 

 the impurity of the materials to which it has been applied. Indeed, 

 it seems that progress in understanding salivary proteins will come 

 only with the development of good methods of separation of the 

 individual proteins that give adequate recognition to the lability 

 of the native proteins. In this chapter we will deal with physical 

 and chemical properties of the bulked or partly purified salivary 

 proteins as well as with the specific protein components detected 

 by enzymatic or other reactions. 



GENERAL PROPERTIES OF SALIVA PROTEINS 



The physical characteristics of saliva are determined by their 

 protein constituents, for example, dog parotid saliva is usually 

 limpid with a viscosity only slightly greater than that of water, 

 whereas submaxillary saliva from the same animal is viscous, sticky 

 and can readily be drawn out into long threads. These salivas con- 

 tain comparable total quantities of protein bound carbohydrate; 

 indeed the concentration in parotid saliva is frequently greater 

 than in submaxillary saliva. Upon standing at room temperature 

 for an hour or two the viscosity of submaxillary saliva usually de- 

 creases considerably so that already under these mild conditions 

 changes in the saliva proteins have occurred. The gelatinous secre- 

 tion of the palatine and sublingual glands represents an extreme 

 of the viscous type of secretion. Ever since the discovery by Tiede- 

 mann and Gmelin (1826) that most of the viscous material of saliva 



169 



