The isolation and composition of the major glycoprotein from human gastric aspirates

The isolation of the principal glycoprotein from human gastric aspirates and the determination of its carbohydrate and amino acid composition is described.Ninety-nine individual gastric aspirates were investigated. Eighty-two were eluted on Bio-gel P150 and the carbohydrate and amino acid composition of each non-retarded fraction was determined. Fifteen of these non-retarded fractions were chromatographed again on Ecteola cellulose. Seventeen aspirates were precipitated with cetylpyridinium chloride. The carbohydrate, amino acid, and sulphate contents of the subfractions eluted on Ecteola cellulose and cetylpyridinium chloride precipitates were determined. The results suggest that the non-retarded fractions are composed of glycoproteins with a constant basic composition but polydisperse with respect to the sulphate contents and the terminal sugar residues which are associated with blood group specificity. It was found possible to correlate and identify in chemical terms the blood group specificity of all the glycoproteins investigated. No significant differences were detected between the carbohydrate and amino acid composition of each of the non-retarded fractions, the subfractions eluted on Ecteola cellulose, and the cetylpyridinium chloride precipitates. The sulphate content of the isolated glycoproteins was found to vary between zero and a sulphate: glucosamine ratio of 2:3. The subfractions of Ecteola cellulose showed that 20-50% of the glycoproteins were sulphated. The data also suggest that the isolated glycoprotein is the principal carbohydrate-containing fraction of the gastric secretion as it contained 68-96% of the total carbohydrate content of the gastric aspirates investigated.