Characterization of a glycopeptide from the proline-rich glycoprotein of human parotid saliva

Glycopeptides (Gp I and Gp II) were prepared from the proline-rich glycoprotein of human parotid saliva by extensive papain-pronase digestion, Sephadex G-25 gel filtration, and DE-52 cellulose chromatography. Their carbohydrate units contained N-acetylgluco-samine, mannose, fucose, galactose and sialic acid. Based upon minimal mol wt calculations, the salivary glycoprotein contained four heteropolysaccharide units. One glycopeptide (Gp I) was homogeneous by N-terminal analysis and descending paper chromatography. Using dansyl-Edman degradation and partial acid hydrolysis coupled with dansylation, the peptide sequence of Gp I was found to be GlyGlyProAsn (CHO)Gln. Alkaline borohydride treatment of Gp I at 80 °C verified a glycosylamine bond between asparagine and N-acetylglucosamine.