how many binding sites for atp are there in pfk
1-phosphofructokinase The regulation of 1-phosphofructokinase occurs primarily by allosteric effectors, and is based on the cell's energy needs. There are two ATP binding sites; a substrate site where the phosphate transfer occurs, and an allosteric site where allosteric regulation occurs. ATP acts as an allosteric inhibitor and when cellular concentrations of ATP are high, and the cell's energy needs are low, the reaction catalyzed by 1-phosphofructokinase is inhibited. When the cell is actively consuming ATP and stores deplete, the concentration of ATP lowers while the concentrations of AMP and ADP increase. AMP and ADP are both positive effectors of 1-phosphofructokinase and bind allosterically to activate the reaction. This activation encourages glycolysis and ATP production.[4] Inhibition can also occur via citrate, a product of glycolysis and intermediate in the citric acid cycle. An increased concentration of citrate indicates the cell is meeting current energy needs, and therefore encourages allosteric inhibition of 1-phosphofructokinase allosterically via ATP.