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Enzymic Mechanism of Starch Breakdown in Germinating Rice Seeds ¹

15. Immunochemical Study on Multiple Forms of Amylase

Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University, Chikusa, Nagoya 464, Japan, Laboratoire de Physiologie des Organes Végétaux, CNRS, 4 ter, Route des Gardes, 92190 Meudon, France

The formation of multiple forms of amylases in germinating rice (Oryza sativa L. cv Kimmaze) grains was examined by means of isoelectric focusing, cross-immunoelectrophoresis, and rocket-line immunoelectrophoresis followed by a reaction of enzymic characterization by using -limit dextrin or starch as substrate. The constituents detected by isoelectric focusing were identified as three electrophoretically heterogeneous antigens. The major -amylase bands A and B corresponded to a same antigen, the main portion of which was produced within 2 days' germination. The bulk of -amylase D appeared between 2 and 4 days' germination. Component E, a debranching enzyme according to its action on the -limit dextrin, already exists in the ungerminated seeds; its amount decreases within the first 2 days of germination and increases again thereafter.

Evidence showing that -amylase (band C) is produced by the scutellum at an early stage of germination was provided. The enzyme appeared in a suspension of the scutellum after a prolonged incubation.