A debranching enzyme of rice seeds. I. A debranching enzyme of rice seeds at milky stage, its purification and substrate specificities.

Abstract

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 α-1, 6-linkages in pullulan or an α-amylolysis product from starch most favorably, several β-limit dextrins from starch or from amylopectin rapidly, and phytoglycogen β-limit dextrin and amylopectin moderately, while it was unable to debranch phytoglycogen. These substrate specificities were similar to those of the so-called “limit de0x-trinases” already reported with respect to several plant sources.