Salivary Mucoproteins

One of the best-known mucins is that obtained from saliva and extracts of the submaxillary and sublingual glands. It is best prepared from neutral extracts of animal glands or from saliva by precipitation with weak acids (pH 2.5 to 3.5). It is purified by dissolution in stronger acids (pH 1 to 1.5) 

Simmons (89) isolated a mucoid (glycoprotein) in fairly good yield from the extracts of pig submaxillary glands by alkaline extraction in the presence of sodium dodecyl sulfate. The product was separated and purified by fractional alcohol precipitation with ethyl and isopropyl alcohols at 

Blood-group specific substances have been isolated in amount of about 3 mg. per 100 cc. from the salivas of persons of the A, B, and 0 types (90). So-called nonsecretors excrete a similar polysaccharide which does not give the serological reactions typical of the blood-specific substances. 

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Gottschalk, A., 1960, Correlation between composition, structure, shape and function of a salivary mucoprotein. Nature 186 949-951. 

G26. Glass, G. B. J., and Boyd, L. J., Studies on dissolved mucin of the gastric juice. IV. Relationship of the mucoid of the visible gastric mucus, its split products, and the salivary mucin to the dissolved gastric mucoproteose and mucoprotein of the gastric juice. Bull. N. Y. Med. Coll. Flower Fifth Ave. Hosp. 12, 1-33 (1949). 

The nature of the proteins involved in mucoproteins and glycoproteins has received some preliminary study (4, 71), A slight amount of evidence exists that the common protein components are albumins and globulins, except in mucous secretions. Pepsin and trypsin hydrolyze many of the mucoproteins or glycoproteins, but salivary mucoid and ovomucoid are quite resistant. At physiological pH (7.25 to 7.30), only fairly basic proteins would be expected to bond with carboxyl groups, and the sulfate bonding would be most probable for the common proteins. 

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