MathBench > Cellular Processes

Enzyme Kinetics

The other intercept

Interestingly, it turns out that the OTHER intercept (the x-intercept) is the negative reciprocal of Km. If you want, you can do a derivation similar to what we did on the last screen to convince yourself that this is true. Or you can just take my word for it.

graph

So now we can put the whole she-bang together. Imagine you are researching the yellowcakease enzyme again (the one that broke the budget before). You set up rooms with 4 different concentrations of yellow cakes. You measure the rate of mush production in each room. You get the data below. What are the Michaelis Menten parameters for this enzyme?

The Original Data
trial 1 2 3 4 5
[S] 10 20 30 40 50
V 21 30 41 45 49
The Transformed Data
trial 1 2 3 4 5
1/[S]
1/V

Vmax:   Km:  

The Plots

 

 

flash arrange the steps
Step 1: take double reciprocals
Step 2: plot double reciprocals
Step 3: draw a best-fit line
Step 4: find the intercepts of the line
Step 5: take the reciprocals of the intercepts to get the values for Vmax and Km.