ISSN:
1573-4986
Keywords:
mucin
;
sialic acids
;
submandibular gland
;
glycoproteins
;
oligosaccharides
;
sialidases
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Two mucins were isolated from bovine submandibular glands and termed major and minor on a quantitative basis. The major mucin representing over 80% of the total glycoprotein fraction contained 37% of its dry weight as protein in contrast to 62% for the minor mucin. Differences in the amino acid composition reflected the higher proportion of typically non-glycosylated peptide in the minor mucin. The molar ratio ofN-acetylgalactosamine to serine plus threonine was 0.82 in major and 0.65 in minor mucins, indicating a lower degree of substitution of potential glycosylation sites in the minor mucin. Differences in the carbohydrate composition were found largely related to the sialic acids, with higher relative amounts ofN-glycoloylneuraminic acid in the minor mucin. In addition, the proportion of di-O-acetylated sialic acids was higher in the major mucin. The rate of sialidase action on the two mucins could be correlated with the content ofN-glycoloylneuraminic acid in each glycoprotein. There was no difference in the type of oligosaccharide found in each mucin and the differences in relative proportions reflected the monosaccharide composition for the two mucins. Gel filtration on Sepharose CL 2B showed a lower molecular weight distribution for the minor in contrast to the major mucin which was partially excluded. Density gradient centrifugation reflected this variation. SDS-PAGE demonstrated a regular banding pattern for the major mucin with a lowest subunit size of 1.8×105 Da and aggregates in excess of 106 Da, while the minor mucin ranged from 3.0 × 105 to 106 Da. The chemical composition of the isolated mucins was compared with previous histochemical analysis of mucin distribution in bovine submandibular glands and indicates a possible cellular location for each mucin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00731345
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