Normally when one studies an enzymatic reaction you need to do the following:
1. The initial rate of the reaction - or initial velocity - Vo - (when you've just combined the enzyme and the substrate) - you measure the amount of product made per unit time right at the beginning of the reaction.
2. You have to do this for each concentration of substrate - this would be a range of substrate concentrations.
3. You plot these on a graph with (substrate, Vo) as your (x,y)
What you will see is a graph that rises from 0,0 and eventually plateaus.
The plateau indicates that the enzyme is saturated with the substrate and is working as fast as it can. This is the maximum velocity or Vmax.
