2.8 Determination of α-glucosidase
The α-glucosidase activity was determined using a modified method of McCue and Shetty (14). A standard reaction solution is prepared by mixing 0.1 ml of 9 mM p-nitrophenol α-D-glucopyranoside and 0.8 ml of 200 mM sodium of acetate buffer at pH 4.6 in a glass tube. The tubes were pre-incubated at 50°C for 5 min before addition of 0.1 ml of the enzyme extract. The reaction tubes were then incubated for a further 30 min. The enzymatic hydrolysis was stopped by addition of 1 ml of 100 mM sodium carbonate, and the samples were clarified by centrifugation at 13,500 rpm at room temperature for 5 min. The released p-nitrophenol in each sample was determined by measuring the absorbance at 400 nm compared with the blank. A standard curve was established using pure p-nitrophenol dissolved in sodium acetate buffer. One unit of α-glucosidase activity is defined as the amount of enzyme that releases 1 µ mol of p-nitrophenol per min at pH 4.6 and 50°C under assay conditions.