# Enzyme X converts substrate S to product P. When the total concentration of X is 1 μM, Vmax and Km are 1.0 x 10^-3 M/s and 0.10 mM, respectively. What is the value for the kcat/Km?

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I'm stuck because my notes indicate that we need to know the concentration of the substrate [S] to apply any of the equations. I know that if [S] >> Km, you can adjust the Michaelis-Menten equation to be (Kcat)(X) = Vmax, but the problem doesn't tell me [S], and when I tried solving for Kcat using the equation above, and then dividing that by the given Km, I didn't get the correct answer. Thanks!

I'm stuck because my notes indicate that we need to know the concentration of the substrate [S] to apply any of the equations. I know that if [S] >> Km, you can adjust the Michaelis-Menten equation to be (Kcat)(X) = Vmax, but the problem doesn't tell me [S], and when I tried solving for Kcat using the equation above, and then dividing that by the given Km, I didn't get the correct answer. Thanks!

##### 1 Answer

#### Explanation:

It depends on some of the simplifying assumptions (or reasons) as shown in the referenced paper.

Other Values and interactive graph here:

http://www.physiologyweb.com/calculators/michaelis_menten_equation_interactive_graph.html