Calulatating VMax and KM ???????

[caroline.123]

Hi, can anyone help I'm calculating KM and VMax values using a standard graph and comparing results to a Lineweaver Burk Plot. My VMax from graph is 0.0286 what is my Km? My 'plot' crosses the y-axis at 34.5 and crosses the x-axis at -7.2, what are the values of VMax and KM? Thanks.

[CaptainPanic]

I think that it's all nicely explained on the wikipedia website:

 

http://en.wikipedia.org/wiki/Lineweaver-Burk_plot

 

You're probably doing this for homework, so I'm not going to give you the answers... but it's really not very hard.

 

The equation you need to solve is:

[math] V = V_{max}\frac{}{K_m + } [/math]

Or (the inverse of that):

[math] \frac{1}{V} = \frac{K_m}{V_{max}}+\frac{1}{V_{max}} [/math]

 

Since you already have the plot, it is quite easy really... (You should realize that one axis is the [math] 1/ [/math] axis, the other the [math] 1/V [/math] axis... it's not a [math] X [/math] and [math] Y [/math] axis)

 

Please note that the Lineweaver Burk plot is a linearisation, and therefore not necessarily correct... especially at low substrate concentrations.