Glycopeptides isolated from ovine submaxillary mucin.

Desialized ovine submaxillary major mucin was digested extensively with pronase. The digestion product was gel-filtered through Sephadex G-25 then fractionated by ion-exchange column chromatography on Hitachi custom resin No. 2614. Of the resulting fractions, the fractions containing relatively simple glycopeptides were purified by rechromatography on the same ion-exchange column, followed by preparative high-voltage paper electrophoresis. The isolated glycopeptides, A12d, A14a, A17c, and B12, were shown to be homogeneous by high-voltage paper electrophoresis at pH 1.9, 3.7, and 6.5 and by paper chromatography. The results of chemical analysis, alkali treatment, determination of the amino acid sequence and digestion with alpha-N-acetylgalactosaminidase of these glycopeptides indicated their structures to be as follows: glycopeptide A12d, O-alpha-N-acetylgalactosaminyl-Ser-Glx-Pro-Gly; glycopeptide A14a, O-alpha-N-acetylgalactosaminyl-Ser; glycopeptide A17c, O-alpha-N-acetylgalactosaminyl-Ser-Gly-Gly-(O-alpha-N-acetylgalactosaminyl-)Thr-Glx; glycopeptide B12, Gly-(O-alpha-N-acetylgalactosaminyl-)-Ser-Ala.