Determination of K_I using a Secondary Plot

1. 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.
2. 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_maxK_I).
   Thus, K_I = Int/Slope = 3 mM.

Back to Enzyme Inhibition: Answer Sheet.