ADP-Glucose Pyrophosphorylase in Wheat Grains

STARCH phosphorylase1,2 was long assumed to be responsible for the synthesis of starch in plants, but developments in the biochemistry of nucleoside diphosphate sugars suggest that most starch is biosynthesized by transfer of a glucose residue from uridine diphosphate glucose (UDP-glucose) or from adenosine diphosphate glucose (ADP-glucose) to a starch primer3. The formation of UDP-glucose is catalysed by UDP-glucose pyrophosphorylase4 which is widely distributed in plants5: