Purification and properties of porcine submaxillary mucin

The mucin of porcine submaxillary glands was purified by precipitation with cetyltrimethylammonium bromide, followed by fractionation with ethanol from a solution in 50% aqueous calcium chloride. The purified product was demonstrated to be homogeneous by electrophoretic and ultracentrifugal analyses at neutral and alkaline pH. The electrophoretic mobilities were −4.9×10 −5 cm. 2v −1 sec. −1 at pH 7.4 and −6.7×10 −5 cm. 2v. −1 sec. −1 at pH 11. The molecular weight was determined to be 830,000 by the ultracentrifugal procedure. The purified mucin had 20% sialic acid, 24% hexosamines, 12% galactose, and 7% fucose (approximate molar ratio 1:1.7:1:0.7), and 40% protein. N-Glycollylneuraminic acid was the predominant sialic acid component, but a small amount of N-acetylneuraminic acid was also present. By column and paper chromatographic methods and ninhydrin degradation of the hexosamines, the principal hexosamine was shown to be galactosamine with only a very small quantity of glucosamine. Analysis of the amino acid constituents showed the characteristic abundance of serine, threonine, glycine, proline, and alanine usually found for mucins and blood group substances. Studies were made of the uniformity of the mucin in different individual glands. The conditions required for the removal of sialic acid from the mucin by mild acid and by neuraminidase were investigated.