They seem to simply be plotting the rate of formation of product at multiple substrate concentrations, however they are well below the enzyme Km (they only go to 60uM when the Km is approx. 1mM). Is this a reliable method for calculating Kcat? And, if so, how do you actually obtain Kcat from a plot like this?
Hi there,
What is actually calculated from this figure is catalytic efficiency which is kcat/Km. The slopeof figure1 is actually Vm/Km and knowing the enzyme concentration used kcat/Km can be calculated as Vm is kcat[E]0. kcat can't actually be determined if Km or Vm is not known
The Michaelis-Menten equation is Rate = Vmax[S]/(Km + [S]). Since in fig. 1a, [S]
I partly agree with Adam Shapiro. However, since the maximal [S] is more than ten times lower than Km, I am afraid that the time course is going to be a simple exponential (S=S0.exp(-Vmax/Km.t), from which it will not be posible to separate Vmax from Km.
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