Biochemistry I Fall Term
Calculations & Graphing

Topic #4: Enzyme Kinetics Calculation

Recommended problems in Campbell, Chapter 5: #21, 22, 24.
Model reaction:     E + S <=> (ES<->EP) --> E + P
The Michaelis-Menten equation is:
vo = Vmax[S]/(KM + [S]) ,  where
vo = the initial velocity;
Vmax = the maximal velocity;
[S] = the substrate concentration;
KM = [S] at half-maximal velocity, i.e.the Michaelis constant.
We want to determine Vmax and KM by measuring the dependence of the initial velocity on the substrate concentration. This is done in three steps.
1. Enter a value for [S] in this box:
[S] = mM
2. For the above value of [A], Calculate vo
vo = mM/min
    (Each calculated vo value has a small "experimental error" added to it.
Tabbing out of the [A] entry slot or clicking anywhere on the page will also calculate vo.)

3. Record the values of [S] and vo you obtain; then graph them on a double reciprocal plot to determine KM and Vmax. You should get enough data so as to have 3 or 4 values of vo, both above and below the KM value.
(Hint: Graph the values you obtain as they are calculated; then as the shape of the curve becomes apparent, choose values for [S] that fall into the appropriate range.)
Answers to this problem.

A sample Answer Sheet for a similar problem shows the format of the results and the graph required.

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