Catalyzes the phosphorylation of D-fructose 6-phosphate to fructose 1,6-bisphosphate by ATP, the first committing step of glycolysis. ATP + beta-D-fructose 6-phosphate = ADP + beta-D-fructose 1,6-bisphosphate + H(+) Allosterically inhibited by ATP. Allosteric ATP-binding requires the presence of the substrate ATP. Inhibited by monovalent cations with ionic radii larger than Na(+) (e.g. K(+), Cs(+)). The monovalent cations increase the affinity of the allosteric site for ATP. PFK-2 is sensitive to inhibition by fructose 1,6-diphosphate. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 3/4. Homodimer. Only 10% of the activity present in the wild-type strain is phosphofructokinase-2. This enzyme is not to be confused with 6-phosphofructo-2-kinase which is also called phosphofructokinase 2. E.coli has two 6-phosphofructokinases enzymes. Belongs to the carbohydrate kinase PfkB family.