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 activated by ADP, AMP, or fructose 2,6-bisphosphate, and allosterically inhibited by ATP or citrate. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 3/4. Homo- and heterotetramers (By similarity). Phosphofructokinase (PFK) enzyme functions as a tetramer composed of different combinations of 3 types of subunits, called PFKM (M), PFKL (L) and PFKP (P). The composition of the PFK tetramer differs according to the tissue type it is present in. The kinetic and regulatory properties of the tetrameric enzyme are dependent on the subunit composition, hence can vary across tissues (Probable). Isoform 2 and isoform 3 interact (via N-terminal testis-specific region) with GSTM5. Isoform 2 and isoform 3 interact (via C-terminus) with HK1 (via N-terminal spermatogenic cell-specific region). Principal piece region of the sperm flagellum. Principal piece region of the sperm flagellum. Isoform 1 is expressed in skeletal muscle (at protein level). Isoform 2 and isoform 3 are testis-specific and are detected in quiescent sperm (at protein level). They are first detected in the cytoplasm of round spermatids and subsequently in the flagellum of elongated spermatids extending into the seminiferous tubule lumen (at protein level). Isoform 2 is expressed at higher level than isoform 3 in testis. Isoform 2 and isoform 3 are first seen on postnatal day 16 corresponding to the age when midpachytene spermatocytes are present in the synchronous first wave of spermatogenesis. Isoform 2 and isoform 3 levels increase substantially between days 14 and 18 and continue to increase to age 30 days of neonatal testis development. GlcNAcylation decreases enzyme activity. Belongs to the phosphofructokinase type A (PFKA) family. ATP-dependent PFK group I subfamily. Eukaryotic two domain clade 'E' sub-subfamily. Intron retention.