So that horizontal green line describes the maximum possible rate at which the enzyme can operate on that particular substrate. And in the previous lecture, when we discussed the turnover number Kcat, we basically gave an equation that describes how to actually obtain the maximum velocity. So we said that v max of an enzyme is equal to the product of the turnover number KCAD and the concentration, the total concentration of the enzyme. And this basically describes that situation when all the active sites in our enzyme mixture are filled with the substrate. This is when the velocity, the rate of the enzyme mixture will be at a maximum. So the enzyme operates at a maximum rate when all the active sites are filled.