Allostenic enzymes at certain piints in the respiration pathway respond to inhibitors and activatovs that hlep set the pace of glycolysis and the Krebe cycle. Phosphofructokinase, the enzyme that catalyzes step 3 of glycolysis, is one such enzyme. It is inhibited by ATP and by citrate. This feedback regulation adjusts the rate of respiration as the cell's catabolie and anabolic demands change.