DEBRANCHING ENZYME OF RICE SEEDS .1. DEBRANCHING ENZYME OF RICE SEEDS AT MILKY STAGE - PURIFICATION AND SUBSTRATE SPECIFICITIES

A debranching enzyme was purified about 100-fold over the crude enzyme solution from non-glutinous rice seeds at the milky stage by using DEAE-, CM-cellulose, and then Sephadex G-100 column chromatography. This disc-electrophoretically homogeneous enzyme showed a specific activity of 16.5 pullulanase units/mg of protein (25°C) with its optimum pH at 5.6. The enzyme debranched the a-1,6-linkages in pullulan or an α-amylolysis product from starch most favorably, several/3-limit dextrins from starch or from amylopectin rapidly, and phytoglycogen/5-limit dextrin and amylopectin moderately, while it was unable to debranch phytoglycogen. These substrate specificities were similar to those of the so-called “limit dex- trinases” already reported with respect to several plant sources. © 1979, by the Agricultural Chemical Society of Japan.