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finding Km & Vmax values

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Mon11
New Zealand

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Status: Frog Egg
 Topic Started by Mon11 on 10/5/2009 14:48 PM

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..

Attached file: Picture 2.png

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DrMobs
Australia

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 Posted By DrMobs on 10/5/2009 15:59 PM

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
New Zealand

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Status: Frog Egg
 Posted By Mon11 on 10/5/2009 22:02 PM

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
Australia

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Status: Frog Egg
 Posted By DrMobs on 10/5/2009 22:45 PM

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
United States

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Status: Protein Chemistry and Bioinformatics Moderator
 Posted By Suola on 10/6/2009 4:17 AM

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,

Certainty of death, small chance of success... What are we waiting for? - Gimli

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