<Tr> <Th> PDB </Th> <Td> RCSB PDB; PDBe; PDBj </Td> </Tr> <Tr> <Th> PDBsum </Th> <Td> structure summary </Td> </Tr> <P> Phosphofructokinase - 1 (PFK - 1) is one of the most important regulatory enzymes (EC 2.7. 1.11) of glycolysis . It is an allosteric enzyme made of 4 subunits and controlled by many activators and inhibitors . PFK - 1 catalyzes the important "committed" step of glycolysis, the conversion of fructose 6 - phosphate and ATP to fructose 1, 6 - bisphosphate and ADP . Glycolysis is the foundation for respiration, both anaerobic and aerobic . 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, a 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 . </P> <Table> <Tr> <Td> β - D - fructose 6 - phosphate </Td> <Td_colspan="2"> Phosphofructokinase 1 </Td> <Td> β - D - fructose 1, 6 - bisphosphate </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="2"> </Td> <Td> </Td> </Tr> <Tr> <Td> ATP </Td> <Td> ADP </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td> </Td> <Td> H O </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="2"> Fructose bisphosphatase </Td> <Td> </Td> </Tr> </Table>

Why is phosphofructokinase a rate-limiting enzyme of glycolysis
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