Seems to be involved in the degradation of glucomannan. ATP + D-fructose = ADP + D-fructose 6-phosphate + H(+) Inhibited by zinc ions. Up-regulated by konjac glucomannan and by cellobiose and mannobiose, the possible degradation products of glucomannan. Repressed by glucose via the carbon catabolite repression system. Also repressed by GmuR. Belongs to the ROK (NagC/XylR) family.