Pfk

Pfk, most commonly referring to phosphofructokinase (PFK), is a central enzyme in glycolysis. It catalyzes the ATP-dependent phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, a committed step that regulates glycolytic flux and energy production in cells.

In vertebrates, the primary catalytic activity comes from PFK-1, which forms a tetramer assembled from subunits encoded by the PFKL, PFKM, and PFKP genes. These subunits can combine to yield isozymes with tissue-specific kinetic properties. PFK-1 is allosterically regulated: it is activated by AMP and fructose-2,6-bisphosphate and inhibited by ATP, citrate, and low pH. Fructose-2,6-bisphosphate, produced by the bifunctional enzyme PFK-2, is a potent activator that links glycolysis to hormonal and metabolic signals.

In bacteria and some other organisms, distinct pfk genes, such as pfkA and pfkB, encode different phosphofructokinases with varying regulatory properties and substrate specificities. pfkA-type enzymes are typically ATP-dependent and responsive to energy state, while pfkB-type enzymes often belong to broader kinase families with alternative regulatory modes.

Clinical and research relevance: hereditary deficiency of PFK-1 causes Tarui disease (glycogen storage disease type VII), a metabolic myopathy characterized by exercise intolerance and impaired glycolysis. Because PFK-1 sits at a key control point in glycolysis, it is a focus in studies of metabolic diseases, cancer metabolism, and metabolic engineering.

Notes: While Pfk most often denotes phosphofructokinase, the acronym can have other context-dependent meanings in different fields.