Salivary mucins

The genes encoding the polypeptide backbones of a number of mucins derived from various tissues (eg, pancreas, small intestine, trachea and bronchi, stomach, and salivary glands) have been cloned and sequenced. These studies have revealed new information about the polypeptide backbones of mucins (size of tandem repeats, potential sites of N-glycosylation, etc) and ultimately should reveal aspects of their genetic control. Some important properties of mucins are summarized in Table 47-8. 

Namavar, F., Sparrius, M., Veerman, E. C., Appelmelk, B. J., and Vandenbroucke-Grauls, C. M. (1998). Neutrophil-activating protein mediates adhesion of Helicobacter pylori to sulfated carbohydrates on high-molecular-weight salivary mucin. Infect. Immun. 66, 444- 7. 

Food is taken into the buccal cavity, where it is masticated by the teeth and mixed with saliva from three pairs of salivary glands. It moistens the food and dissolves some molecules enabling them to interact with the taste receptors on the tongue. Saliva contains Na% Cl and HCOs ions and a protein, mucin, which is a component of mucus that lubricates the chewed food on its way down the oesophagus. The pH of saliva is about 7.8, which neutralises acid formed by bacteria in the mouth this protects tooth enamel... 

Saliva. The salivary glands produce a slightly alkaline secretion which—in addition to water and salts—contains glycoproteins (mucins) as lubricants, antibodies, and enzymes. a-Amylase attacks polysaccharides, and a lipase hydrolyzes a small proportion of the neutral fats. a-Amylase and lysozyme, a mu-rein-cleaving enzyme (see p. 40), probably serve to regulate the oral bacterial flora rather than for digestion (see p. 340). 

One exception to the generalization that the two systems work in opposition to each other is secretion by the salivary glands both sympathetic (noradrenergic) and parasympathetic (cholinergic) activation of these glands leads to an increase in the flow of saliva. However, the nature of the saliva produced by the two systems is qualitatively different. The saliva produced by activation of the sympathetic system is a sparse, thick, mucinous secretion, whereas that produced by parasympathetic activation is a profuse, watery secretion. 

Effect on secretions Atropine reduces the various body secretions e.g. sweat, salivary, bronchial and lacrimal etc. It also reduces the volume and total acidity of gastric secretion and, reduce the secretion of mucin and enzymes in the gastric secretions induced by cholinergic drugs. 

Therkildsen, M. H., Mandel, Y., Thorn, J., Christensen, M., and Dabelsteen, E. 1994. Simple mucin-type carbohydrate antigens in major salivary glands. J. Histochem. Cytochem. 42 1251-1259. 

Submucosa. The submucosa is a relatively dense connective tissue with a few accessory salivary glands (mucus acinus).102 The saliva is secreted primarily by parotid, submandibular, and sublingual glands at a rate of 0.5 to 2 L/day.94 Apart from water, saliva is composed of electrolytes, mucin (forms mucus with water), amylase, lysozyme (a bacteriostatic enzyme), IgA antibodies, and metabolic wastes such as urea and uric acid.18 The pH of saliva varies between 6.8 and 7.2.96... 

Some studies have been made relating specifically to astringency. Some of these studies have focused directly on interactions between tannins and salivary proteins [21, 23, 25, 46, 50-53], and on the changes in saliva protein composition after interaction with tannins [15, 38, 54, 55]. Other studies have correlated the sensorial astringency with protein-tannin interactions [45, 56, 57]. In fact, the astringency felt when sampling different tannin solutions can be correlated with the ability of these tannins to precipitate proteins. This effect has been observed with several proteins such as mucin [45], ovalbumin and gelatin [57], bovine semm albumin (BSA), and salivary proteins [58]. 

Apart from salivary proteins, other proteins have been used in studies of kind mucin [56], gliadin [49], pl-glycosidase [32, 59], hemoglobin [60], and BSA [24, 35-37, 48, 61-64]. Other proteins have been used because of certain characteristics that make them similar to proline-rich proteins (PRPs), like casein [33, 65], gelatin [42, 49, 65-67], and polyproline [34, 66, 68]. Although it is not a protein, the polymer polyvinylpolypyrrolidone has also been used in these studies [68, 69]. 

Gerken T.A. (1993) Biophysical approaches to salivary mucin structure, conformation and dynamics. Crit Rev Oral Biol Med 4, 261-270... 

Wickstrom C. and Carlstedt I. (2001). N-terminal cleavage of the salivary MUC5B mucin. 

Sialic acids are a family of nine-carbon acidic monosaccharides based on 3-deoxy nonulosonic acid (Fig. 17.4, also see Chapter 5). In 1952, the biochemist Gunnar Blix introduced the term sialic acid from the Greek aaXia (salia) or saliva after isolating this molecule from the salivary gland mucin. Sialic acid is now the generic term for the family that includes derivatives with a C5-amino substituent called neuraminic acid. Neu5Ac (5) is the type of sialic acid found in humans [47],... 

T. A., Biophysical approaches to salivary mucin structure, conformation, and dynamics, Crit. Rev. Oral Biol. Med. 4, 261-270, 1993 Dodd, S., Place, G.A., Hall, R.L., and Harding, S.E., Hydrodynamic properties... 

The basis of bacterial adhesion is given by the acquired pelhcle formation on tooth surfaces. This pelhcle is a thin ( 0.5-l pm) layer of several sahvary proteins with calciumhydroxide-binding properties. The most important such proteins are salivary amylase, cystatins (S, SA, and SN type), histatin (HRPl), mucine (MGl), acidic PRPs, statherin, and immunoglobulins (slgA) (4, 7). 

Acute stress Decrease of sIgA, Increase of amylase, salivary chaperon Hsp70, stress hormones Prompt changes of mucins adhesive properties... 

C22a. Code, C. F., Ratke, H. V., Livermore, G. R., Jr., and Lundberg, W., Occurrence of gastric secretory inhibitor activity in fresh gastric and salivary mucin. Federation Proc. 8, 26-27 (1949). Abstr. 

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). 

Saliva, pH 7, contains ptyalin (salivary amylase), digests starches. Mucin, a glycoprotein, lubricates food and may interact with drugs... 

Karlsson et al. [85] reported the stmctural characterization of fifty different neutral 0-linked glycans ranging from di- to nonasaccharides from salivary mucin MUC5B, using negative-ion LC-MS and MS-MS. Primary sequence information could be derived from Y- and Z-ions. In addition, some linkage information could be deduced from additional fragmentation pathways. 

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