176 Organic Constituents of Saliva 



of the high mobility mucoproteins found on electrophoresis of 

 saliva is a sialomucin. The inhibitory action of mucin and other 

 neuraminic acid containing substances on the haemaglutination 

 produced by some viruses (e.g. influenza) is due to the presence in 

 these organisms of an enzyme (neuraminidase) with an affinity 

 for neuraminyl terminal groups and the power to hydrolyse the 

 glucoside linkage joining neuraminic acid to the next carbohydrate 

 residue. Mucin prevents haemagglutination by providing neura- 

 midyl groups which compete with those on the red cells for the 

 virus neuraminidase (Gottschalk, 1954, 1958). 



BLOOD GROUP SUBSTANCES 



Soluble blood group specific substance is present in human sub- 

 maxillary saliva (Landsteiner and Harte, 1941). This substance has 

 the same characteristics as the agglutinogen on the erythrocyte 

 and may be demonstrated by direct precipitin reaction with type 

 specific sera or by inhibition of red cell agglutination. It is not 

 precipitated by trichloracetic, picric or sulphosalicylic acids but is 

 quantitatively precipitated by alcohol (see comprehensive review 

 by Kabat, 1956). 



Blood group substances are present in the submaxillary saliva 

 from all individuals but if the red cells have the Le a antigent the 

 saliva contains Le a substance rather than A, B or O (H). Purified 

 blood group substances from saliva seem to be typical fucomucins 

 and there is rather little difference in gross chemical composition 

 between A, B, AB, H and Le a substances (Morgan and Watkins, 

 1959). The purified materials contain 14-19 per cent of fucose and 

 24-32 per cent of hexosamine. By controlled hydrolysis, some 

 disaccharides are produced and may be isolated. For instance, the 

 following disaccharides were isolated from Group A substance: 



1. a-galactosyl 1 ->3 N-acetyl galactosamine. 



2. /^-galactosyl 1 ^3 N-acetyl galactosamine. 



3. /^-galactosyl i->4 N-acetyl galactosamine. 



4. a-N-acetylgalactosaminyl 1 ->3 galactose. 



5. /?-N-acetylgalactosaminyl 1 -x$ galactose. 



6. a-fucosyl 1 ^6 N-acetylglucosamine. 



This type of work may lead to the establishment of sugar sequences 

 in the blood group substances comparable to that already success- 

 fully achieved for the amino-acid sequences in a number of pro- 



