Effects of Bay m 1099, an α-Glucosidase Inhibitor, on Starch Metabolism in Germinating Wheat Seeds

To examine the significance of α-glucosidase in starch metabolism in vivo, wheat seedlings and seeds were treated with Bay m 1099 (Miglitol, N-hydroxyethyl-1-deoxynojirimycin), an α-glucosidase inhibitor. Bay m 1099 did not affect germination, but it inhibited growth of seedlings at the high dosage (100 μg/ml medium). Treatment of normally grown seedlings with Bay m 1099 (10 and 100 μg/ml) decreased α-glucosidase activity with a dose response and caused accumulation of maltose in tissues with decreases in glucose. The decrease in glucose formation would inhibit plant growth, which was observed particularly at higher dosages of the inhibitor. When wheat seeds were treated with Bay m 1099 at 10 μg/ml for 4 days, under which the growth of the plants after germination was minimized, the induction of α-glucosidase, but not amylase, in kernels was considerably suppressed during germination and maltose metabolism to glucose was disturbed. In addition, the Bay m 1099 treatment decreased the initial rate of starch degradation by 48%, compared with the control. These results suggest that wheat α-glucosidase participates in maltose hydrolysis as well as in the onset of starch degradation with collaboration of amylase.