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How to Calculate Vmax and Km from Enzyme Activity Data using a Lineweaver-Burk Plot

The activity of an enzyme was determined in the presence and absence of a suspected inhibitor. You can see the activity data in the attached Word document. Plot the data using the double reciprocal plot (Lineweaver-Burk) to determine whether the suspected inhibitor acts noncompetitively, competitively, or uncompetitively.

Calculate Vmax and Km in the absence and presence of the inhibitor.


Solution Preview

Here's how to go about solving the problem:

Step One:
Manually, transfer the data into Excel and create reciprocal data, i.e. 1/[S] and 1/v.

Step Two:
Create a graph of both data sets using the Chart Wizard. Choose the "XY (Scatter)" Chart type.

Step Three:
Add a trendline to the data by right clicking on the data points for each set. The drop down menu will have "Add Trendline" in it. Click on that. Choose the linear type of trendline. Go to the "Options" tab and check the box that says, "Display equation on chart." We will need to see the mathematical equation describing the line. This will be necessary when calculating Km, etc.

Step Four:
When you do this, you will notice that the trendline doesn't continue as far to the x-axis as ...