Abstract
A chromatographic procedure for purification of the proteins in human parotid saliva has been developed. The eluates of a Sephadex G-150 and two ion exchange columns have been analyzed simultaneously by several physical and chemical tests; these include three optical properties of proteins, assays for neutral sugars, sialic acid and zinc, and disc gel electrophoresis. The ratios of the different variables have been used to determine the homogeneity and complexity of the protein distribution in the various peaks of the chromatographic eluates. By chromatographic methods, it has been possible to purify a glycoprotein with unusual staining characteristics and amino acid composition. Glycoproteins with similar properties comprise a major portion of the proteins in parotid saliva and appear to constitute a family of related proteins which differ in molecular size, carbohydrate and sialic acid content, and electrophoretic mobility. The fractionation of several enzymes in parotid saliva is also reported.
Highlights
The eluates of a Sephadex G-150 and two ion exchange columns have been analyzed simultaneously by several physical and chemical tests; these include three optical properties of proteins, assays for neutral sugars, sialic acid and zinc, and disc gel electrophoresis
A family of glycoproteins with very unusual amino acid composition, little or no absorbance at 280 nm, and which stain pink-violet with Coomassie brilliant blue R-250 has been resolved in Fractions II, III, and V from Sephadex G-150
As we assume, the proteins in these fractions represent a family of glycoproteins, they would constitute about 85% of the protein of human parotid saliva calculated from their relative A215 absorbance
Summary
The eluates of a Sephadex G-150 and two ion exchange columns have been analyzed simultaneously by several physical and chemical tests; these include three optical properties of proteins, assays for neutral sugars, sialic acid and zinc, and disc gel electrophoresis. Glycoproteins with similar properties comprise a major portion of the proteins in parotid saliva and appear to constitute a family of related proteins which differ in molecular size, carbohydrate and sialic acid content, and electrophoretic mobility. Further fractionation on DEAE-Sephadex A-50 of one of the six fractions and subsequent fractionation on carboxymethyl (CM)-cellulose resulted in the separation of a series of glycoproteins with similar but very unusual amino acid compositions and a gradation in carbohydrate and sialic acid content. Proteins in human parotid saliva are related to each other, but differ somewhat in charge, size, carbohydrate, and sialic acid content. Several enzymes and a zinc protein have been shown to be present in parotid saliva and have been purified
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