
Determination of K_{I} using a Secondary Plot
 Double Reciprocal Plot: 1/v_{o} vs. 1/[A].
The above graph is the same as that on the Enzyme Inhibition: Answer Sheet page. The bottom (blue) line corresponds to the data without added I. The intercept and slope yielded, V_{max} = 0.5 mM/min and K_{M} = 2 mM.
The top two lines (green and red) correspond to the lines with 2 mM and 5 mM added [I], respectively.
 Secondary Plot: Slopes vs. [I].
The slopes from the above double reciprocal plot are plotted in a secondary plot (or "replot") vs. the [I]'s used.
The intercept of this graph is, K_{M}/V_{max}.
The slope of this graph is, K_{M}/(V_{max}K_{I}).
Thus, K_{I} = Int/Slope = 3 mM.
Back to Enzyme Inhibition: Answer Sheet.
