In a study of enzyme activity, the initial rate of reaction (y, in μMoles/min) is measured with various substrate concentrations (x, in mMoles/L) but the same enzyme concentration. The reaction rate measurements have an accuracy of 0.05 μMoles/min.
In 1913 Leonor Michaelis and Maud Menten presented a theory which predicted an inverse x & y relationship (the Michaelis-Menten equation):
1/v = (1 + Km/[S] )/vmax
where v is the rate of reaction, vmax is the maximum possible rate of reaction, Km is the Michaelis-Menton constant, and [S] is the concentration of the substrate. Comparison of the Michaelis-Menten equation with the generic inverse x & y relationship, suggests:
A = 1/vmax
B = Km/vmax
so
Km=B/A
X (mMoles/L) | Y (μMoles/min) |
---|---|
9.0E-2 | 1.05 |
0.174 | 1.59 |
0.19 | 1.75 |
0.33 | 2.25 |
0.37 | 2.42 |
0.51 | 2.63 |
0.91 | 3.18 |
1.01 | 3.15 |
1.74 | 3.49 |
2.7 | 3.68 |