Phosphofructokinase (PFK) is the most important regulatory enzyme (EC 2.7.1.105) of glycolysis. It is an allosteric enzyme made of 4 subunits and controlled by several activators and inhibitors. This leads to a precise control of glucose and the other monosaccharides galactose and fructose going down the glycolysis pathway.

This enzyme catalyzes what is considered the first "committed" step of glycolysis, since it is not only irreversible, but also because the original substrate is forced to proceed down the glycolytic pathway after this step. Before this enzyme's reaction, glucose-6-phosphate can potentially travel down the pentose phosphate pathway.

PFK converts fructose 6-phosphate and ATP to fructose 1,6-bisphosphate and ADP. The enzyme has two sites with different affinities for ATP which is both a substrate and an inhibitor.

See also:

• PFK2 (converts fructose 6-phosphate to fructose 2,6-bisphosphate)
• PFP (reversibly interconverts fructose 6-phosphate and fructose 1,6-bisphosphate using inorganic pyrophosphate (rather than ATP)
• fructose bisphosphatase (hydrolyses fructose 1,6-bisphosphate to fructose 6-phosphate)