GLYCOPROTEINS IN THE HEAT-STABLE AND ACID-STABLE FRACTION OF OVINE MILK

Affinity chromatography on a concanavalin A-Sepharose support was used to isolate two glycoprotein fractions from a heat- and acid-stable fraction of ovine milk. One of these glycoprotein fractions was purified by rechromatography on DEAE-cellulose to essentially a pure protein yielding a single band on gel electrophoresis. The apparent Mr of this glycoprotein (GP2) as estimated by electrophoresis was 50500. It contained 8.88% carbohydrate and 0.61% P. The other glycoprotein fraction (GP3) contained 0.53% P and 17.76% carbohydrate including sialic acid, mannose, galactose, fucose, galactosamine and glucosamine. It appeared on electrophoresis in acrylamide gels as a slow-moving broad band. On similar treatment in the presence of sodium dodecyl sulphate it revealed four glycoprotein zones with apparent Mrof 15200, 18300, 23500 and 25300. Both GP2 and GP3 contained low amounts of aromatic and sulphur-containing amino acid residues and large amounts of Asp, Glu, Ser and Leu. GP3 is similar in some respects to the bovine milk heat- and acid-stable fraction constituent, component 3. © 1990, Proprietors of Journal of Dairy Research. All rights reserved.