Localization of Pullulanase- and α-glucosidase-like Immuno-reactivity in Non-glutinous Rice Grains during Cooking

The pullulanase and α-glucosidase in brown rice is predominately found in the endosperm of rice grains of Koshihikari and Nipponbare cultivars. However, the exact localization of these enzymes in the endosperm layers is not clear. To investigate enzyme localization in non-glutinous brown rice, immuno-fluorescence detection of these enzymes was carried out using frozen sections of rice grains (Koshihikari, Nipponbare and Milkyqueen cultivars). While pullulanase-like immuno-reactivity was dominantly detected in amyloplasts, α-glucosidase-like immuno-reactivity was mainly detected along endosperm cell walls among the three non-glutinous cultivars. Immuno-reactivity of both enzymes overlapped in the aleurone layer and embryo among the three cultivars. During rice cooking, pullulanase-like immuno-reactivity partly overlapped with α-glucosidase-like immuno-reactivity along endosperm cell walls among the three cultivars. These results indicate that each enzyme has a unique localization, and these unique localizations are common among the three non-glutinous cultivars.