Mucin polysaccharides

The reactants are then mixed in various proportions, and the sedimentation ratio (scompiex/smucin)—the ratio of the sedimentation coefficient of the complex to that of the pure mucin itself—is used as the measure for mucoad-hesion. The ultra-violet absorption optics on the XL-A or XL-1 ultracentrifuge have been used as the main optical detection system. Although the polysaccharide is generally invisible in the near UV ( 280 nm), at the concentrations normally employed the mucin—in uncomplexed and complexed form—is detectable. 

Deoxy-L-galactose (L-fucose) HO H H HO HaC—C—C—C—C-—CHO H HO HO H plant gums seaweeds blood polysaccharides sea-urchin eggs frog-spawn mucin... 

Figure 14.2 Representative oligosaccharide structures found on mammalian glycoproteins and glycolipids. The complex oligosaccharides may be bi-, tri-, or tetra-antennary the branches may be more or less elongated with 1—>4 linked lactosamine units, and they may or may not be sialylated. The SLex, Lea, and Leb structures represent the different blood group determinants often present on lipids, and the elongated core 2 structure is a mucin-type glycosylation. Proteoglycans have a common core to which a variety of linear acidic polysaccharides are attached.

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). 

Modification of this procedure was applied to the analysis of neutral and amino sugars in mucins [440]. A mixture of 0.2% of ethylene glycol succinate, 0.2% of ethylene glycol adipate and 1.4% of silicone XE-60 was used as the stationary phase and the analysis was effected with temperature programming at l°C/min from 150 to 205°C. Similar results could be obtained, however, on a column packed with 3% of OV-225. Partially ethylated alditol acetates were used to determine the components of polysaccharides [441],... 

The reaction of partially purified, lima-bean lectin with hog gastric-mucin type A substance exemplified the precipitin-like curve obtained for lectin-polysaccharide or -glycoprotein reactions.103 Classical precipitin-curves between purified components II and III and type A blood-group substance were also obtained.151,199 Maximal precipitation of component II (equivalence) occurred at a lower ratio of A substance per mole of protein than for component III. Under conditions where type A substance precipitated 90% of the lectin, types A2 and B precipitated151,199 66 and 13%, respectively, of component II, and 21 and 0% of component III. Neither of the lima-bean lectins precipitated with type O blood-group substance. 

As we know at present, the mucoproteose fraction includes the following materials (1) most of the gastric fucomucins, as well as some of the blood group substances, i.e., most of the neutral polysaccharides of the dissolved mucin fraction linked to their peptide moiety, (2) y-globulin and probably also P-globulin, which pass into the gastric juice from the serum (G16, G42, Hll, H20, H55) and probably account for the presence of mannose in this fraction (Gll), (3) some of the pep-tidic degradation products of serum albumin and visible mucus, which are partly dialyzable (G16, K2), (4) native intrinsic factor, the related primary vitamin Bi2 binder, and tertiary vitamin Bia binder related to the neutral mucosubstances (G14, Ul, U2). 

It has been thought (H38, H46, H47) that methods based on quantitation of the polysaccharide moiety of gastric mucin would be more specific for the assay of mucosubstances. This leads, however, to many difficulties as well, and is not acceptable if one does not subject the mucosubstances to prior fractionation by chemical or physicochemical means (see Section 2.4). 

Meyer et ah (M37) isolated two different types of carbohydrate material from hog gastric mucin. One of them had equimolecular amounts of glucosamine, hexuronic acid, acetyl groups, and sulfate, which was therefore thought to be mucoitin sulfuric acid. The second was a neutral polysaccharide, which will be discussed below. Wolfrom and Rice identified (W23) the hexuronic acid in this preparation as D-glucuronic acid. 

Meyer (M34, M35) classified the neutral polysaccharide of hog gastric mucin as mucoid, since it contained over 4% hexosamine. This probably corresponded to the mixture of the carbohydrate moieties of fuco-mucin and sialomucin, whereas his acidic mucopolysaccharide (mucoitin sulfuric acid) consisted perhaps of a mixture of acidic aminopolysac-charides (mucopolyuronides) and possibly some sialic acid. 

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