Catalyzes the phosphorylation of fructose to fructose-6-P. Has also low level glucokinase activity in vitro. Is not able to phosphorylate D-ribose, D-mannitol, D-sorbitol, inositol, and L-threonine. ATP + D-fructose = ADP + D-fructose 6-phosphate + H(+) Catalytic efficiency with D-fructose as substrate is 55-fold higher than that with D-glucose. Belongs to the ROK (NagC/XylR) family. Extended N-terminus.