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(+) Exists as both a dimer and a tetramer and the equilibrium between the active tetramer and inactive dimer is regulated by several allosteric effectors, including protein concentration, pH, ADP, ATP, AMP-PNP, and F6P. ADP, ATP, low pH, and AMP-PNP shift the equilibrium toward the dimer. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 3/4. Homotetramer (By similarity). Homodimer, inactive form (PubMed:29940104). Component of a possible RNA degradosome complex composed of cshA, eno, pfkA, pnp, rnjA, rnjB, rnpA and rny. Interacts specifically with RNA helicase CshA. Belongs to the phosphofructokinase type A (PFKA) family. ATP-dependent PFK group I subfamily. Prokaryotic clade 'B1' sub-subfamily. Truncated N-terminus.