finding Km & Vmax values

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Mon11
Mon11's picture
finding Km & Vmax values

Hello everyone,

 I've got  data on Excel, one column is for time (min) the other column is for substrate concentration (mmol/L), how can I calculate the velocity using these two given data by Excel so I can calculate Vmax & Km?

ThanQ..

DrMobs
DrMobs's picture
Look up Michaelis-Menten

Look up Michaelis-Menten kinetics in Wikipedia. You need the enzyme activity (V, in eg abs/unit time; fluorescence/unit time), not time itself. Then you construct a Lineweaver-Burk plot (1/V vs 1/[S]). The y intercept is 1/Vmax and the x intercept is -1/Km.

Mon11
Mon11's picture
 Thank you DrMobs,

 Thank you DrMobs,

apparently you didnt get what i want exactly, I need to do that by Excel, without using graphical methods, and I dont have the right formula to calculate the velocity from the time & concentration given, so ill be able to calculate Vmax & Km 

I hope someone can help me with that :(

DrMobs
DrMobs's picture
The time (min) column is not

The time (min) column is not velocity. Do you have more information?
When you have velocity:
Make columns of the reciprocals.
Use the INTERCEPT (c) and SLOPE (m) functions of Excel to get the line parameters (mx+c)
The reciprocal of the INTERCEPT will be Vmax.
Work out what x is when y=0.
Take the negative reciprocal of this to get Km.
(I hope this isn't an assignment or exam question).

Suola
Suola's picture
Mon11,

Mon11,

By googling "how to calculate km and vmax excel", gives you as a first hit:

http://www.biotech.sfasu.edu/bt/BTC560/HOW%20TO.htm

Cheers,