(1) The increase of [
14C] glucose incorporation from ADP-[
14C] glucose into 7M urea-treated starch was observed, and that from UDP-[
14C] glucose was significant in 5M urea-treated starch. (2) Search for the fate of the incorporated glucose into intact starch granules revealed that [
14C] glucose from radioactive ADP-glucose was found mainly in the outer layer of granules which was insoluble in 10M urea. On the other hand, radioactivity from UDP-[
14C] glucose was incorporated into both the inner (urea soluble fraction) and the outer layer. (3) Soluble fraction after pullulanase treatment of 7M urea treated starch incorporated [
14C] glucose into ethanolprecipitated fraction from UDP-]
14C] glucose, not from ADP-[
14C] glucose. (4) These findings indicate that starch synthetase bound to starch granules toward ADP-glucose is localized in a starch granule, and starch synthetase toward UDP-glucose was solubilized by urea/pullulanase treatment of starch granules.
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