ISOLATION AND PARTIAL CHARACTERIZATION OF HUMAN AND PORCINE GASTRIC MUCINS

High-molecular-weight water-soluble mucin fractions were isolated from the gastric mucosal layer of human and porcine stomachs by column chromatography on Sepharose CL-4B followed by cesium chloride density gradient centrifugation, and their amino acid and carbohydrate compositions were analyzed. They had similar, but slightly different amino acid compositions characteristic in high content of serine and threonine residues. The carbohydrate content was about 80% by weight in both fractions, and the compositions were similar but somewhat different especially in fucose and glucosamine contents. Further, the molecular sizes of the porcine mucin and apomucin fractions were analyzed by gel filtration on a TSKgel G5000PW column. The results suggested that the major portion of the porcine mucin may be oligomers composed of two glycoprotein components with apparent molecular weights of about 600 K and 60 K cross-linked together or separately by intermolecular disulfide bonds.