FUNCTION Catalyzes the phosphorylation of D-fructose 6-phosphate to fructose 1,6-bisphosphate by ATP, the first committing step of glycolysis.ACTIVITY REGULATION Allosterically activated by ADP, AMP, or fructose 2,6-bisphosphate, and allosterically inhibited by ATP or citrate.PATHWAY Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 3/4.SUBUNIT Homo- and heterotetramers (By similarity). Phosphofructokinase (PFK) enzyme functions as a tetramer composed of different combinations of 3 types of subunits, called PFKM (where M stands for Muscle), PFKL (Liver) and PFKP (Platelet). The composition of the PFK tetramer differs according to the tissue type it is present in. In muscles, it is composed of 4 PFKM subunits (also called M4). In the liver, the predominant form is a tetramer of PFKL subunits (L4). In erythrocytes, both PFKM and PFKL subunits randomly tetramerize to form M4, L4 and other combinations (ML3, M2L2, M3L). In platelets, brain and fibroblasts, PFK contains a higher proportion of PFKP subunits. The kinetic and regulatory properties of the tetrameric enzyme are dependent on the subunit composition, hence can vary across tissues (Probable).PTM GlcNAcylation decreases enzyme activity.MISCELLANEOUS In human PFK exists as a system of 3 types of subunits, PFKM (muscle), PFKL (liver) and PFKP (platelet) isoenzymes.SIMILARITY Belongs to the phosphofructokinase type A (PFKA) family. ATP-dependent PFK group I subfamily. Eukaryotic two domain clade 'E' sub-subfamily.