Question

The figure above is a Lineweaver-Burk plot of P. furiosus PFK with [fructose-6-P] held constant and [ADP] as the variable substrate (dot), in the presence of 5mM ATP (O), or in the presence of 5 mM AMP (X; Tuininga et al., 1999).

How does the addition of ATP affect PFK affinity for ADP?

Answer 1

Phosphofructokinase (PFK) is a key enzyme of glycolysis, which converts fructose 6 phospahte to fructose 1-6 bisphosphate by transferring phosphate group to fructose from ATP. The addition of ATP decreases the affinity between Phosphofructokinase and ADP because Phosphofructokinase is an enzyme which is involved in phosphorylation of substrate by transferring phosphate from ATP or ADP. The chance of transfer of phosphate to substrate from ATP is high compared to ADP as PFK has the high affinity towards ATP. When there is depletion of ATP in the vicinity then PFK chooses ADP as phosphate donar. So, as the concentration of ATP increases, affinity between Phosphofructokinase and ADP decreases.