Lipids associated with dog gastric mucus glycoprotein

The lipid content and composition of dog gastric mucus and its mucus glycoprotein before and after Pronase digestion was investigated. The mucus and the purified glycoprotein, in its intact and degraded form, were extracted with chloroform/methanol and the lipids contained in the extracts were quantitated. The lipids accounted for 18.9% of the dry weight of mucus and their content increased to 29.4% in the purified glycoprotein and fell to 27.8% following digestion of the glycoprotein with Pronase. In comparison to mucus, lipids associated with undegraded glycoprotein contained 1.7 times more phospholipids and 1.8 times more glycolipids, and were virtually free of glycosphinoglipids. Pronase digestion of the glycoprotein led to 2.3-fold decrease in phospholipids and 1.3-fold increase in glyceroglucolipids. The results suggest that the interaction of mucus glycoprotein with phospholipids involves its nonglycosylated region.