An enzyme's saturation behavior means that beyond some substrate concentration

Core Concept

At a fixed enzyme concentration and under fixed conditions, increasing substrate eventually occupies nearly all available active sites. The reaction rate then approaches Vmax, so adding still more substrate has little effect. Increasing the amount of active enzyme can raise Vmax, but enzyme activity can also change with factors such as temperature, pH, inhibitors, and covalent regulation; 'only more enzyme' is too absolute.