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Negative Vmax and Km values

I've used Excel to plot a Lineweaver Burk graph for data that was given to us (made up data but supposed to be realistic).
The equation of the line was y = 3.231x - 12.851 (with the presence of an inhibitor).
So I ended up with Vmax: -0.078 and Km: -0.251
I know it's not possible to have negative values for Vmax and Km so I'm just wondering where I've gone wrong here. I plotted the LB graph and clicked "display equation" on Excel so it automatically gave me that equation. Why is it coming up as -12.851 rather than a positive y intercept? How can I fix this?

I obtained Vmax: 0.20 and Km: 0.07 from the Michaelis Menten graph (which was hand-drawn).
Hi,
did you ever find an answer to this?


Original post by Petulia
I've used Excel to plot a Lineweaver Burk graph for data that was given to us (made up data but supposed to be realistic).
The equation of the line was y = 3.231x - 12.851 (with the presence of an inhibitor).
So I ended up with Vmax: -0.078 and Km: -0.251
I know it's not possible to have negative values for Vmax and Km so I'm just wondering where I've gone wrong here. I plotted the LB graph and clicked "display equation" on Excel so it automatically gave me that equation. Why is it coming up as -12.851 rather than a positive y intercept? How can I fix this?

I obtained Vmax: 0.20 and Km: 0.07 from the Michaelis Menten graph (which was hand-drawn).
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Avatar for Petulia
Petulia
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Original post by becka_murphy
Hi,
did you ever find an answer to this?


Sorry I've just looked back at my coursework now and I can't remember how I solved it, but I did change the equation of the line to y = 3.231x + 12.851 instead of - 12.851. So I used + 12.851 in my calculations and got positive values in my results.
Thank you! I’ve literally it the same coursework question haha!

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