Structural Characterization and Hypoglycemic Activity of a Glycoprotein Extracted from Auricularia Auricula

Glycoproteins are special proteins and important nutrients for hypoglycemic activity. However, the structure of <i>Auricularia Auricula</i> glycoprotein (AAG) and the stability of its hypoglycemic activity during simulated digestion (including saliva, gastral and intestine digestion) in vitro are still unknown. In this study, AAG-3 was isolated from <i>Auricularia Auricula</i>. SDS-PAGE, UV spectrum, FTIR, amino acid composition, dichroic spectrum and SEM were used to characterize its structure. The hypoglycemic activity of AAG-3 during in vitro digestion was investigated via inhibition of α-amylase and α-glucosidase activities, as well as glucose consumption, glycogen content and related enzyme activity in insulin-resistant HepG2 cells. Structural characterization showed that AAG-3 with a Mw of 18.21 kDa had an O-type glycopeptide bond and typical functional groups of glycoproteins. AAG-3 contained 18 kinds of amino acid and many α-helixes and β-turns, and its microstructure was sheet-like. With the simulated digestion of AAG-3 in vitro, the inhibition of α-amylase and α-glucosidase activity as well as the glucose consumption, glycogen content and HK and PK enzyme activities in insulin-resistant HepG2 cells were significantly increased. Therefore, AAG-3 has a potential role in reducing blood glucose levels and improving insulin resistance and can be used as a potential micronutritional supplement for diabetic patients.