Studies On Isolation And Identification Of ACE Inhibitory Peptides From Oyster And Their Properties

Oysters,is one kind of marine organism,full of nutrition,which contains a variety of biological activities.In this study,there were four aspects of Oysters studied,including preparation,purification,characterization and properties of angiotensin converting enzyme(ACE)inhibitory peptides from oyster.the main results were as follows:(1)Hippuric method was used for evaluating the inhibitory activity of angiotensin converting enzyme(ACE)from extracts of Oysters.Papain was selected for the optimal enzyme from five proteases based on ACE inhibition rate and the degree of hydrolysis.The hydrolysis conditions were optimized by single factor and orthogonal experiments response.The results showed that the optimum conditions of hydrolysis were solid-liquid ratio(m/v)1:8,1.5% of papain,60 min of hydrolysis time,at the temperature of 65? and p H 6.0.When the mass concentration was 5 mg/m L,the inhibition rate of products on ACE was 63.3%.(2)The enzymatic hydrolysates were modified using Plastein reaction on the basis of the enzymatic hydrolysis.There were two parameter free amino acids and ACE inhibition rate to examine the influence of the enzyme variety,substrate concentration,enzyme concentration,temperature and time of reaction on the modified enzyme.In the research,the optimum condition was substrate concentration 40%,1% of neutral protease,at the temperature of 30?,2.5h of hydrolysis time,p H7.The mass concentration was 5 mg/m L,the inhibition rate of ACE was 82.31%,19% higher than the unmodified.(3)ACE inhibitory peptide of Oysters was isolated and purified by ultrafiltration and Sephadex LH-20 gel chromatography column.Purification of ACE inhibitory peptides was promoted by HPLC system.After ultrafiltration,the oyster hydrolysate was divided into four components,of which the mass was less than 3k Da,and in this part the inhibition activity of ACE was the highest,and the inhibition rate was 64.4%(5mg/m L).The hydrolysate of Oyster Protein Hydro lysate less than 3 k Da was separated by Sephadex LH-20 gel chromatography column,the ACE inhibitory activity of F2 and F5 was higher,which was up to 78.9% and 76.7%,respectively.After the analysis of the semi-preparative RP-HPLC,the ACE inhibitory peptides of F2 were purified into four components,the mass concentration was 5 mg/m L,the highest inhibition rate was 54.89%.Mass spectrometry analysis of F5 showed that 168 peptides were obtained.Seven potentially active peptides were selected,as follows: FYYDGKVVKLSEPAEEVA,GFLFLQCGLTL,VSLSGFQYSGFL,MDFSPDGTKVA,KYDISYIVNSVL,SKLMVTEIRRRASNQSTEAA,WMPYFGPFM.The specific ACE inhibitory activity needs to be further determined.(4)In vitro simulated gastrointestinal digestion revealed that the peptides were stable after digestion.In addition,the water absorption ability of peptide power was 0.35g/g and oil absorption was 0.74g/g.Its emulsifying ability was 20 cm2/g and emulsion stability was well at p H 5 and 10.