Purification And Characterization Of A Glycoprotein From Fruits Of Fructus Corni

α -Amylase inhibitors are a kind of organic compounds which can be found in microorganisms, animals and plants. They can be potentially used as medicines of diabetes owing to inhibiting starch from being hydrolyzed in the digestive tracts, and their genes can also be used as insect-resistant genes in transgenic plant.An inhibitor(CoGP) of α -amylase was isolated from fruits of Fructus Corni by using D₁₀₁ macro-reticular resine, ion exchange chromatography with SP Sepharose and gel chromatography with Sephacryl S-300. This inhibitor was proved to be a kind of glycoprotein by analyzing the properties of gel filtration with Sephacryl S-300 and ultraviolet absorption spectrum. The homogeneity of this glycoprotein was proven by gel filtration on Sephacryl S-300 ,PAGE and agar gel electrophoresis. Under reducing conditions ,it showed two bands on SDS-PAGE corresponding to molecular weight of 62.0 kD and 56.8 kD respectively. The molecular weight of the native glycoprotein was 158.9kD estimated on Sephacryl S-300. The results above suggest that the glycoprotein is composed of two units. The purified CoGP's carbohydrate content is about 51%. Characterization of this glycoprotein by IR analysis showed the typical absorption of polysaccharide and indicated the presence of β -glycoside linkage.During preincubation of α -amylase and inhibitor, the glycoprotein inhibited porcine pancreatic α -amylase in an anticompetitive manner. After preincubationwith pepsin, the activity of CoGP was losed, which will probably limit CoGP's therapy in diabetes.