May play an important role in maintaining the flux of carbon towards starch formation. ATP + D-fructose = ADP + D-fructose 6-phosphate + H(+) Glycan biosynthesis; starch biosynthesis. Expressed in swelling stolons and, at higher levels, in developing tubers. Low levels found in leaves and stems from tuberizing plants. Belongs to the carbohydrate kinase PfkB family.