Phosphofructokinase
Because phosphofructokinase (PFK) catalyzes the ATP-dependent phosphorylation to convert fructose-6-phosphate into fructose 1,6-bisphosphate and ADP, it is one of the key regulatory and rate limiting steps of glycolysis. PFK is able to regulate glycolysis through allosteric inhibition, and in this way, the cell can increase or decrease the rate of glycolysis in response to the cell’s energy requirements. For example high ratio of ATP to ADP will inhibit PFK and glycolysis. The key difference between the regulation of PFK in eukaryotes and prokaryotes is that in eukaryotes PFK is activated by fructose-2,6-bisphosphate. The purpose of fructose-2,6-bisphosphate is to supersede ATP inhibition, thus allowing eukaryotes to have greater sensitivity to regulation by hormones like glucagon and insulin.
fructose biphosphates
F2,6BP is one of the most important compounds involved in allosteric regulation of glycolysis and gluconeogenesis.
F2,6BP is made by action of the enzyme phosphofructokinase-2 (PFK2).
In this reaction, fructose-6-phosphate (F6P) is converted to F2,6BP by addition of a phosphate from ATP to position 2 of the molecule.
F2,6BP is broken down to F6P by action of the enzyme fructose-2,6-bisphosphatase, which hydrolyzes the phosphate from position 2, regenerating F6P.
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