Acute glucose fluctuation during the postprandial period causes a risk for type 2 diabetes mellitus (T2DM).α-Glucosidase inhibitors have been approved as therapeutic agents for diabetes.In the present study,a protein with α-glucosidase inhibitory activity from Flax (Linum usitatissimum) seeds was isolated using a one-step purification with Q-Sepharose4B column,followed by Sephacryl S-200 size-exclusion chromatography.It was identified as a trypsin inhibitor,named L.usitatissimum trypsin inhibitor (LUTI).The half maximal inhibitory concentration (IC50) of LUTI was 113.92 μM for α-glucosidase and 6.17 μM for trypsin.Lineweaver-Burk kinetic experiment showed that the protein exhibited two distinct inhibitory modes,a competitive inhibitor type for α-glucosidase and a non-competitive type for trypsin.The interaction between LUTI and α-glucosidase was detected through gel filtration chromatography and dynamic light scattering.Increased glucose consumption and lactic acid production were also observed following LUTI treatment in Caco-2 and HepG2 cells.LUTI inhibits not only the activity of trypsin but also the activity of α-glucosidase.It is expected that LUTI will become an oral hypoglycemic polypeptide drug for T2DM.