178 Organic Constituents of Saliva 



In the parotid gland no specific staining for blood group substances 

 was found. It appears therefore that in man the blood group sub- 

 stances are specifically secreted by the mucous cells of the sub- 

 maxillary gland. Blood group substances have also been reported 

 in the saliva of the horse, pig, cow, rabbit, sheep, goat, dog, ele- 

 phant, guinea pig and monkey. In man secretion appears to be 

 limited to the A, B, O and Le a substances. 



AMYLASE 



The discovery of amylase in saliva is usually attributed to 

 Leuchs (1831) but was actually described earlier by Tiedemann 

 and Gmelin (1826). Amylase is present in the saliva of many 

 species including man, apes, guinea pig, mouse, rat and rabbit but 

 is absent or present only in very low concentrations in the parotid 

 and submaxillary saliva of the dog, cat, cow, horse, sheep and goat. 

 The absence of the enzyme in the saliva of some herbivores sug- 

 gests that salivary digestion of starches is not of great importance. 

 In the parotid saliva of man amylase is the major single protein 

 component (Ferguson, Krahn and Hildes, 1958; Kostlin and 

 Rauch, 1957; Patton and Pigman, 1957). Amylase is present in 

 human saliva at birth but its concentration is very low and only 

 reaches near adult levels towards the first year of life (Nicory, 1922 ; 

 Mayer, 1929). In human parotid saliva, the concentration of amy- 

 lase is virtually independent of the rate of saliva secretion (Fergu- 

 son, Krahn and Hildes, 1958) but a transient reduction in salivary 

 amylase occurs in man after internal radiation to the gland with 

 I 131 (Schneyer, 1953). In the mouse the amylase content of the 

 salivary glands is only slightly dependent on sex or maturity, sug- 

 gesting that it is not secreted by the granular tubule (see page 31) 

 (Junqueira, Fajer, Rabinovitch and Frankenthal, 1949; Reynaud 

 and Rebeyrotte, 1949). 



Amylase is readily crystallized from saliva following successive 

 acetone and ammonium sulphate precipitations (Meyer, Fischer, 

 Staub and Bernfeld, 1948) and is a carbohydrate-free protein 

 (Muus, 1954) with a pH optimum of 6-9 and a requirement for 

 chloride ions in order to reach full activity. Bromide, nitrate and 

 iodide will replace chloride but yield a lower activity (Bernfeld, 

 Staub and Fischer, 1948). There is only one amylase in saliva, be- 

 longing as do all other animal amylases to the class of a-amylases 

 which specifically split 1 : 4-glycoside linkages. In linear starch and 



