Rice Bifunctional α-Amylase/Subtilisin Inhibitor: Characterization, Localization, and Changes in Developing and Germinating Seeds

1 January 1998

journal article
Published by Taylor & Francis in Bioscience, Biotechnology, and Biochemistry

Vol. 62 (5) , 978-985
https://doi.org/10.1271/bbb.62.978

Abstract

A bifunctional α-amylase/subtilisin inhibitor (RASI) was purified to electrophoretic homogeneity from rice (Oryza sativa L.) bran. Its molecular mass was 21 kDa by SDS-PAGE and its isoelectric point was 9.05. Purified RASI inhibited subtilisin Carlsberg strongly and inhibited α-amylase from germinating rice seeds weakly. It inhibited rice α-amylase more than barley α-amylase, and the inhibition of rice α-amylase was greater at higher pHs. RASI did not inhibit trypsin, chymotrypsin, cucumisin, or mammalian α-amylase.The RASI was in the outermost part of the rice grain and its subcellular site seemed to be aleurone particles in aleurone cells. SDS-PAGE and western blotting showed that RASI was synthesized in the late milky stage in developing seeds, and it remained fairly constant during the first 7 days of germination.

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