Question

If an enzyme has a Km of 10 micromolar, what fraction of the enzyme is active at 100 micromolar substrate concentration?

Answer 1

Km means Michealis constant is concentration of substrate at which the half of the enzyme is active to it's maximum activity (Vmax). Means the concentration of substrate at which half of the enzyme sites are active. And Vmax is the double of the Km value.

So, sample enzyme has Km 10micromoles, that is half Vmax is 10 micromoles. Means Vmax is 20 micromoles. And we are provided 100 micromoles substrate that means saturated substrate solution for enzyme activity.

So, in this case all the active sites of enzyme are active. 100 percent fraction is active. And enzyme work with it's full efficiency.