Salivary and Mucous Glycoproteins

Glycoproteins in the sputum of patients with chronic bronchitis have been solubilized and then fractionated on Sepharose 4B into components of high and low molecular weight The sputum of bronchial patients contains more components of low molecular weight. Mucins from macroscopically healthy areas of the bronchial mucosa of six adults are anionic and contain residues of sialic acid and sulphate. Affinity chromatography on immobilized Ricinus communis lectin has enabled the mucins and other glycoproteins secreted by human bronchia to be characterized.  

spectra of proline-rich glycopeptides (mol. wts. 6—12 x 10 ) from human parotid saliva have been examined, and it was suggested that these glycopeptides are the precursors of glycoproteins of higher molecular weight.  

Lafltte, G. Lamblin, M. Lhermitte, P. Humbert, P. Degand, and P. Roussel, Carbohydrate Res., 

The structure and biosynthesis of mucins have been reviewed. 

Purified human asthmatic bronchial mucin has a minimum molecular weight of 1.8 X10 with aggregates of 1 X 10 or greater.Oligosaccharide chains are linked iV-glycosidically via 2-acetamido-2-deoxy-D-galactosyl residues to L-serine or L-threonine residues, which account for approximately one of every five amino-acids in the protein. 

The extraparotid saliva of Macaque monkeys contains a glycoprotein (mol. wt. 9.6 X 10 ) capable of inhibition of the precipitation of calcium phosphate. The major glycoproteins obtained from Bonnet monkey cervical mucous of the peri-ovulatory and of the pre-menstrual phases differ mainly in the point of linkage of the terminal neuraminic acid residues and of the substitution of the 

2- acetamido-2-deoxy-D-galactosyl residues linked to the protein chain. Differences in the levels of heterogeneity and in N-terminal amino-acid residues were also detected in the two groups of glycoproteins. 

On the basis of the structural identity of the newly formed oligosaccharide unit arising from the in vitro D-galactosylation of desialylized ovine sub-maxillary mucin, the porcine submaxillary gland galactosyltransferase has been defined as a UDP-D-galactose Q -D-2-acetamido-2-deoxygalactosyl-protein 

Hudson, L. J. Wegner, J. M. Wingate, and K. L. Carraway, Comp. Biochem. Physiol, 

Mucus from human gastric mucosa had been purified to immunological and electrophoretic homogeneity. The piuified material exhibited blood-group activity. 

The binding of calcium ions by the mucins of rat small intestines probably involves sialic acid and carboxy-groups, which co-operate to produce a contraction or folding of the molecule on binding of the cation.  

The enzymic removal of sialic acid from bovine cervical mucus has been used in an attempt to establish a molecular basis for the rheological properties. The storage modulus, viscosity, and c.d. spectrum were essentially unchanged, indicating that the removal of terminal sialic acid residues does not affect the physical structure of the glycoprotein to any appreciable extent. 

The binding of cholera toxin by salivary mucin was inhibited by free sialic acid or by treatment of the mucin with neuraminidase, whereas no inhibition was achieved in parallel experiments with gastric and intestinal mucins.  

The possibility that disulphide bonds create a network in mucous gels has been examined, using the sputum of patients with chronic bronchitis or bronchorrhoea. Fragments released by tryptic digestion of human neutral bronchial mucin contained the antigenic determinant, part of which is composed of carbohydrate residues.  

Sodium thiocyanate has been used to disperse canine tracheal mucus, affording dissociation of up to 100%, with a high retention of elasticity and no demonstrable changes in the shapes or sizes of the component glycoproteins.  

Schauer, J. Haverkamp, M. Wember, J. F. G. Vliegenthart, and J. Kamerling, European 

Roukema, C. H. Oderkerk, and M. S. Salkinoja-Salonen, Biochim. Biophys. Acta, 

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Salivary Binding Proteins. Salivary proteins that bind to hydroxyapatite and which may be important in pellicle formation include,(2 ) (i) mucous glycoproteins (MW=3-5... 

Salivary, Mucous, and other Mammalian Body Fluid Glycoproteins... 

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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