Phosphofructokinase
From Free net encyclopedia
- PFK (Poulet Frit Kentucky) is also the name for KFC in French-speaking Quebec, Canada.
Phosphofructokinase (PFK) is the most important regulatory enzyme (Template:EC number) 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.
Regulation
PFK-1 is inhibited by its product, ATP and from the TCA, citrate. It is activated by high-levels of AMP, and the most potent activator is fructose-2,6-bisphosphate, which is produced by PFK-2 from the same substrate.
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)