Lipids associated with rat small-intestinal mucus glycoprotein.
The lipid content and composition of rat small-intestinal mucus, and the purified mucus glycoprotein before and after Pronase digestion were investigated. The mucus, obtained by the instillation of intestine with 2M NaCl, was fractionated on Bio-Gel A-50 in the presence of 6M urea and the mucus glycoprotein free of noncovalently bound protein was isolated. A portion of the purified glycoprotein was subjected to Pronase digestion to yield glycopeptides. The native mucus, and the purified glycoprotein and glycopeptides were extracted with chloroform-methanol, and the lipids contained in the extracts were analyzed. The lipids accounted for 17.6 of the dry weight of mucus, 26.4 of the mucus glycoprotein, and 25.3% of the glycopeptides. In comparison to mucus, the lipids associated with mucus glycoprotein contained 1.9 times more phospholipids and 2.1 times more glycolipids, showed a 26% increase in neutral lipids, and were virtually free of glycosphingolipids. Treatment of the purified glycoprotein with Pronase led to a moderate (22.3%) loss in neutral lipids, 4.3-fold decrease in phospholipids, and 52.3% increase in glyceroglucolipids. The results indicate that while the interaction of mucus glycoprotein with phospholipids involves its Pronase-susceptible region, the interaction with glyceroglucolipids occurs in the glycosylated region of the glycoprotein that is resistant to proteolysis.
D000818:Animals; D002784:Cholesterol / Q000302:isolation & purification; D005230:Fatty Acids, Nonesterified / Q000302:isolation & purification; D005989:Glycerides / Q000302:isolation & purification; D006017:Glycolipids / Q000302:isolation & purification; D006020:Glycopeptides / Q000032:analysis; D006023:Glycoproteins / Q000302:isolation & purification*; D007413:Intestinal Mucosa / Q000032:analysis*; D008055:Lipids / Q000302:isolation & purification*; D008297:Male; D009093:Mucus / Q000032:analysis*; D010743:Phospholipids / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains
D005230:Fatty Acids, Nonesterified; D005989:Glycerides; D006017:Glycolipids; D006020:Glycopeptides; D006023:Glycoproteins; D008055:Lipids; D010743:Phospholipids; D002784:Cholesterol