Preparation And Characterization Of α- Glucosidase Inhibitory Peptide From Squid Liver Protein

In this study, squid liver was used to produce proteins and bioactive peptides. The purpose of this study was to isolate bioactive peptide with α-glucosidase(AG) inhibitory activity from squid liver protein hydrolysis and the stability and inhibition kinetics of this fraction were also studied. The main contents and results are shown as following:1. Squid liver proteins were hydrolyzed in six different enzymatic systems. The hydrolysate by pepsin treatment showed the highest α-glucosidase inhibitory activity. The hydrolyzation conditions on producing AG inhibitory peptide from squid liver proteins with pepsin treatment were optimized. The best enzymolysis condition is: 37 ℃ enzymolysis 12 h, 3 % of enzyme and substrate mass ratio, 0.4 % substrate concentration, p H 3, the half inhibition concentration of enymoltsis products is 1.5 mg/m L2. Squid liver protein hydrolysates was sequentially separated with Sephadex LH-20、DEAE-650 M anion exchange column and PR-HPLC, and only fraction A1 with α-glucosidase inhibitory activity was obtained. Its half inhibitory concentration(IC50) is 0.056 mg/m L, increasing 27 times than the original hydrolysates activity.3. Squid liver protein hydrolysates was separated by Sephadex LH-20 preliminary separation, and fraction Ⅲ with the highest AG inhibitory activeness was obtained. Thermal stability of fraction Ⅲ was good. It was stable when p H was between 5.0 and 9.0, the retention of inhibitory activity was abovt 95%. But its inhibitory activity was significantly reduced at extreme p H conditions. And fraction Ⅲ in vitro was treated through artificial gastric juice and artificial intestinal juice, the retention of inhibitory activity was 90% and 80%, most of the inhibitory activity can get a better retention. Fraction Ⅲ is a typical non-competitive inhibition for AG.