Well, Km has two meanings. One meaning of the Km basically tells us it's the substrate concentration that gives us rate of VMAX divided by two. But the other meaning of Km, basically Km describes how attracted that enzyme the active side is to that substrate. So if we have a very high Km value, what that means is that active side is not very likely to bind onto that substrate. But if the Km value is low, that means there will be a very good binding that takes place between the substrate and that particular active side. So if we take a look at the following ratio a very high Km value basically means this ratio will be small.