Catalyzes the phosphorylation of D-fructose 6-phosphate, the first committing step of glycolysis. Uses inorganic phosphate (PPi) as phosphoryl donor instead of ATP like common ATP-dependent phosphofructokinases (ATP-PFKs), which renders the reaction reversible, and can thus function both in glycolysis and gluconeogenesis. Consistently, PPi-PFK can replace the enzymes of both the forward (ATP-PFK) and reverse (fructose-bisphosphatase (FBPase)) reactions. beta-D-fructose 6-phosphate + diphosphate = beta-D-fructose 1,6-bisphosphate + H(+) + phosphate Non-allosteric. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 3/4. Homodimer. Belongs to the phosphofructokinase type A (PFKA) family. PPi-dependent PFK group II subfamily. Clade 'B2' sub-subfamily.