So this is the enzyme that catalyzes step three. This is the enzyme that catalyzes step one. And this is the enzyme that catalyzes step ten. And the reason our cells use these three enzymes is because these catalyze Irreversible steps in glycolysis. Now, phosphor fructoclinase, as was said, is the most important regulatory enzyme and that's because it catalyzes the Irreversible commitment step. So once the step actually takes place, this fructose one six bisphosphate that is transformed from fructose six phosphate by phosphorutokinase has to go on and complete the process of glycolysis.