Study On The Extraction And Purification, Composition Structure And Biological Activity Of ?-amylase Inhibitor Glycoprotein In White Kidney Beans

A homogeneous glycoproteinα-amylase inhibitor (α-AI) was extracted and purified from white kidney beans (Phaseolus vulgaris. L) by a series of modern technologies. The biochemical characterization, ultrafiltration technology , hypoglycemic, hypolipidemic activity and structure/function relationship were systematically studied in this dissertation.Anα-AI was purified from white kidney beans (Phaseolus vulgaris. L) by a series of chromatography. It was a 36000Da homogeneous glycoprotein and was effective against porcine pancreatic amylase and presented as an uncompetitive inhibition. The activity ofα-AI was stable to pH and temperature.Theα-AI glycoprotein contained 88.2% protein and was rich in aspartic acid, glutamic acid, serine and threonine. The carbohydrate moiety consisted of Man, Glc, Gal and Xyl in a mole ratio of 2.42:1.50:1.52:1.00. The sugar chain was connected byαglucosidic bond. The glycan and the core protein backbone were connected by O-linkage.The study of relationship between structure and function showed there was no inhibitory activity when using protein or sugar chain along; only when protein and sugar chain were linked together, it presented inhibitory activity.Compared with inorganic ceramic membrane ultrafiltration, Organic membrane ultrafiltration was more suitable for concentratingα-AI glycoprotein from solution of white kidney beans. The optimum parameters were as follows: retentive molecule 10000Da, pressure 0.8 MPa, solution concentration 7%(1:15), temperature 35℃; natural pH. In this condition, the flux of membrane was 35.6 L/m~2h, the volume was concentrated 8.3 times, retentive ratio of polysaccharide was 20.1%, retentive ratio of protein was 72.7%, extracting ratio ofα-AI was 80.6%.The study of acute toxicity, hypoglycemic and hypolipidemic activity ofα-AI from white kidney beans were as follows:α-AI was nontoxic;α-AI could significantly reduce fast blood sugar, decrease the postprandial rise in blood concentration and improve sugar tolerance in alloxan-dependent diabetic model rats;α-AI could significantly reduce the concentration of TG, TC, LDL-C and increase the concentration of HDL-C in serum of hyperlipidemia model rats.