| Diabetes is known as a health killer and poses a great threat to the human body to some extent.At present,diabetes can only be treated but not be cured.Long term hyperglycemia in diabetics can lead to a series of complications,including chronic cardiovascular disease,chronic renal failure,retinal damage and even loss of life.Studies have been done to prevent glucose from entering the blood circulation and cause hyperglycemia by inhibiting glucose production enzyme(alpha glucosidase and DPP-IV)in vivo.The inhibition of the enzyme comes from biological reactions,so the target is clustered in bioactive peptides derived from natural plant and animal proteins.Compared with the protein,this small peptide has many biological activities,which has no complex space structure,stable physical and chemical properties.Also small molecular fragments are easily absorbed by the human body.It provides a safe and effective new way for the treatment of diabetes.The aim of this study is to use natural protein as the raw material to prepare peptides with hypoglycemic activity by enzyme method.In this study,the optimization conditionsfor the preparation of peptides were determined with the inhibition of the activity of α-glucosidase.The results showed that the peptide also had antioxidant and hypotensive activity,besides the digestion process had a certain advance effect on them.In this study,we purified,identified,and verified the activity of the peptide which inhibited the alpha glucosidase activity.Using whey protein,mung bean protein and soy protein as the peptide sources,α-glucosidase inhibitory activity and hydrolysis degree were used to screen different peptides.The inhibitory activity of α-glucosidase from soy protein by alkaline protease hydrolysis of 8 h was the highest,and the inhibition rate was 53.79 ± 1.14%.Therefore,theoptimization conditions of the preparation peptide was determined to be thatthe soybean protein(2%)was hydrolyzed for 8 h by the alkaline protease(6000U/g substrate),and the degree of hydrolysis was 36.84 ± 1.20%.The molecular weight distribution of the prepared soy peptide was measured,andthe results showed that the the small molecule with a molecular weight range of 180-1000 Da accounted for 72.23%,and the amino acid analysis showed that the hydrophobic amino acid content accounted for 27.57% in this peptide,which play an important role inα-glucosidase inhibitory activity.And the inhibition rate of dipeptidyl peptidase IV(DPP-IV)was 40.85 ± 0.74%,and the inhibition rate of ACE enzyme was 35.33 ± 1.64%,it also showed that peptides possessed bioactivity of the hydroxyl radical scavenging and the total reduction ability.For the digestive characteristics of peptide,we studied the effect of peptide on the inhibitory activity of α-glucosidase,DPP-IV and ACE after gastrointestinal digestion.The results showed that the three biological activity increased in various degrees after gastrointestinal digestive stimulation,and the inhibition rate ofα-glucosidase increased from 29.04 ± 1.82% to 77.64 ± 1.53%,DPP-IV enzyme inhibition rate increased from 40.85 ± 0.74% to 47.94 ± 1.02%;the inhibition rate of ACE enzyme increased from 20.31 ± 1.66% to 51.43 ± 1.27%.In order to identify the amino acid sequence of the peptide with the α-glucosidase inhibitory effect,ion exchange chromatography DEAE-52 and Sephadex-15 are successively separated to obtain the polypeptide that inhibits α-glucosidase.Tandem mass spectrometry(LC-MS/MS)was used to characterize the amino acid sequence of chromatographic separation and purification system.Three novel peptides with theα-glucosidase inhibitory LLPLPVLK,SWLRL and WLRL were obtained.The IC50 value were 237.43 ± 0.52 μmol/L,182.05 ± 0.74 μmol/L,and 165.29 ± 0.74 μmol/L,respectively.Therefore,peptides hydrolysed from soy protein are promising natural ingredients for nutraceutical applications assisting in the management of diabetes. |
PDF Full Text Request