Phosphofructokinase

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Phosphofructokinase

Bacterial Phosphofructokinase: 3rd glycolysis enzyme (smaller than in Eukaryots). In yellow=sugars; in red=ATP-ADP; starred=regulatory sites (PDB code=4pfk) (more details...)

"PFK" redirects here. PFK (Poulet Frit Kentucky) is also the name for KFC in French-speaking Quebec, Canada.

Phosphofructokinase (PFK) is the most important regulatory enzyme (EC 2.7.1.11) 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, or be converted to glucose-1-phosphate and polymerized into the storage form Glycogen.

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.

[edit] Regulation

PFK1 is inhibited by its product, ATP and citrate (from the Citric acid cycle). It is also inhibited by low pH to prevent the accumulation of hydrogen ions in muscle.

PFK1 is activated by high concentration of AMP. It is also activated by high-levels of AMP but the most potent activator is fructose 2,6-bisphosphate, which is also produced from fructose-6-phosphate by PFK2.

PFK is inhibited by glucagon. This is important in gluconeogenesis

[edit] 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)

v • d • e  Glycolysis Metabolic Pathway

Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate Glyceraldehyde 3-phosphate ATP ADP ATP ADP NADP+ + Pi NADPH + H+ + 2 Pi H2O NADP+ + Pi NADPH + H+ 1,3-bisphosphoglycerate 3-phosphoglycerate 2-phosphoglycerate Phosphoenolpyruvate Pyruvate Acetyl Co-A ADP ATP H2O ADP ATP CoA + NADPH + H+ NADP+ + CO2 2 2 2 2 2 2 ADP ATP H2O ADP ATP

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