Confirmation of the Presence of Amylase-binding Protein on Maize Starch Granules and Characterization of the Enzyme

Abstract

　Maize starch granules were used as the sample, and the decomposition reaction mediated by alpha-amylase molecules that did not contain the starch-binding domain (SBD) was elucidated. The starch surface protein (SSP) was found to cover the surface of the maize starch granules. We found that decomposition of maize starch granules by SBD-free alpha-amylase increased in the presence of SSP. When SSP of the maize starch granules was dissolved by treatment with SDS solution, the decomposition rate of starch granules decreased. The decomposition rate recovered when SSP was added to the SDS-treated starch. When SSP was added to the SDS-treated maize starch granules, the rate of alpha-amylase-mediated decomposition recovered. We clearly show that SSP is the maize storage protein zein, which can bind with alpha-amylase and shows film formation capability.