Well, because they essentially regulate virtually irreversible processes that only take place in one direction. So let's take a look at phosphor fructosekinase. This enzyme catalyzes step three and this happens to be the most important enzyme, why? Well, because it regulates the commitment step of glycolysis. So it transforms fructose six phosphate into fructose one six bisphosate. When we're at this stage the fructose six phosphate before it has been transformed, it has a choice.