白豆中α-淀粉酶抑制剂的分离及其活性研究

采用乙醇分级沉淀、CMII纤维素离子交换柱色谱及凝胶柱色谱,从白豆中纯化得到一种α- 淀粉酶抑制剂(α-AI),经SDS-PAGE及Sepharose CL-6B柱色谱鉴定其为结构均一的糖蛋白.该糖蛋白中蛋白质含量为88.2%,氨基酸组成主要为天冬氨酸、谷氨酸、苏氨酸及丝氨酸.糖链部分单糖组成为甘露糖、葡萄糖、半乳糖和木糖,其摩尔比为2.42∶1.50∶1.52∶1.00.糖和蛋白质结合的糖肽键类型为O-糖肽键.白豆α-AI使用剂量为150 mg·kg-1体重,连续使用7 d时,α-AI可明显降低高血糖大鼠的空腹血糖;使用剂量为300 mg·kg-1时,对高血糖大鼠的糖耐量具有明显的改善作用.研究结果表明,从白豆中分离得到的淀粉酶抑制剂对高血糖大鼠具有明显的降血糖功能,其作为一种安全、天然的降糖药物具有良好的开发前景.

Isolation and activity of an α-amylase inhibitor from white kidney beans

An α-amylase inhibitor (α-AI) was isolated from white kidney beans (Phaseolus vulgaris. L) by ethanol fractional precipitation, ion exchange chromatography and gel filtration column chromatography. It was a homogeneity glycoprotein demonstrated by SDS-PAGE and gel filtration on CL-6B. The glycoprotein contained 88.2% protein and was rich in aspartic acid, glutamic acid, leucine, threonine and serine. The carbohydrate moiety was consisted of Man, Glc, Gal and Xyl in a mole ratio of 2.42∶1.50∶1.52∶1.00. The glycan and the core protein backbone was connected by O-linkage as determined by β-elimination reaction. The continuous oral administration of the α-AI (150 mg·kg-1·d-1 ) for 7 days can lower fasting blood glucose and 300 mg·kg-1 ·d-1 α-AI for 7 days can improve the sugar tolerance on alloxan-dependent diabetic model rats. The result showed the α-AI obtained from white kidney beans had good hypoglycemic effect on alloxan induced diabetic rats and may have high potential pharmaceutical value as a regulative digestive-starch degradation in patients suffering from diabetes.