Preparation Of Malt Root Polypeptide And Its Inhibition On ?-glucosidase Activity

Malt root is the main by-product of beer industry.Every year,more than 100,000 tons of malt root waste are produced in China,which contains 30%of high quality protein.Malt root is a cheap and widely-sourced protein raw material.At present,only a small amount of malt root is used for animal feed or other purposes,most of which are treated as waste.It has great prospects and practical significance to utilize and develop malt root protein.The prevalence of diabetes is increasing year by year due to poor dietary habits and increased life pressure.Prevention and treatment of diabetes has become an urgent and arduous task.Alpha-glucosidase inhibitors are a class of drugs that regulate postprandial blood sugar in diabetic patients.They are widely used,but they are expensive and have side effects such as stomach distension.Therefore,the development of more efficient and safe natural alpha-glucosidase inhibitors is the focus of functional food research and development.In this paper,malt root polypeptide with alpha-glucosidase inhibitory activity was obtained from malt root by enzymatic hydrolysis and purification,and its characteristics were studied,which provided useful reference for the further development and utilization of malt root.Malt root was used as raw material,enzymatic hydrolysis of various proteases was carried out,and the best enzymatic hydrolysis process was determined by single factor experiment,with the inhibition rate of alpha-glucosidase in vitro as the index.After being purified by macroporous resin and Sephadex column chromatography,the malt root polypeptide MRP3-1was obtained,and its amino acid composition and content were analyzed,and enzyme inhibition kinetics was analyzed.To study the stability of MRP3-1,the influencing factors of its activity and the interaction with other alpha-glucosidase inhibitors,the main conclusions are as follows:?1?Taking the inhibition rate of alpha-glucosidase as an index,five proteases were selected to enzymatically hydrolyze malt root,and alkaline protease was selected as the most active hydrolysate.Through single factor experiments,the optimum hydrolysis conditions were determined as follows:0.4%alkaline protease?52?,pH 10.0?,solid-liquid ratio of 1:20,and hydrolysis time of 3.0 h.The yield of polypeptides in the enzymatic hydrolysate was10.76%+0.75%determined by Flynol method,and the IC₅₀ value for the activity of alpha-glucosidase was 2.89 mg/mL.?2?The hydrolysate of malt root was purified by AB-8 type macroporous adsorption resin and Sephadex Sephadex G-50 column chromatography,and the best component MRP3-1 was obtained after purification by two steps.The IC₅₀ value for the activity of alpha-glucosidase was 0.77 mg/mL,and the polypeptide content in MRP 3-1 freeze-dried powder reached89.36%+1.56%.The inhibition kinetics analysis showed that MRP 3-1 had a reversible competitive inhibition on alpha-glucoside,and the inhibition constant Ki was 0.49 mg/mL.?3?MRP3-1 has a good temperature stability,and its alpha-glucosidase inhibitory activity is relatively strong in alkaline conditions,but weakened in high salt concentration and the presence of Cu²⁺,Fe³⁺.Fructose,citric acid and sodium benzoate have little effect on the activity.MRP3-1 has antagonistic effect with dihydromyricetin and luteolin,but has synergistic effect with acarbose.