This invention relates to isolated nucleic acid fragments encoding all or a substantial portion of a corn 4- alpha -glucanotransferase. The invention also relates to the construction of chimeric genes encoding all or a portion of a corn 4- alpha -glucanotransferase, in sense or antisense orientation, wherein expression of the chimeric gene results in production of altered levels of corn 4- alpha -glucanotransferase in a transformed host cell.