Catalyzes the phosphorylation of the ketose sugar fructose to fructose-1-phosphate. ATP + beta-D-fructose = ADP + beta-D-fructose 1-phosphate + H(+) Requires potassium. Inhibition by ADP. kcat is 7.6 sec(-1). Carbohydrate metabolism; fructose metabolism. Homodimer. Most abundant in liver, kidney, gut, spleen and pancreas. Low levels also found in adrenal, muscle, brain and eye. The disease is caused by variants affecting the gene represented in this entry. More widely distributed but with a low expression level. KM=7 mM for D-fructose (at 25 degrees Celsius). KM=036 mM for Mg-ATP (at 25 degrees Celsius). kcat is 6.9 sec(-1). Belongs to the carbohydrate kinase PfkB family.