Figure 3.
β-Lapachone inhibits IDO1 activity through uncompetitive inhibition. Enzyme assays with purified recombinant huIDO1 were performed in the presence of varying concentrations of L-Trp and β-lapachone and the concentration of the product kynurenine was measured at 15 minutes. (A) Michaelis-Menton nonlinear regression plot of substrate-velocity curves at the five different inhibitor concentrations. These data best fit an uncompetitive inhibition model with a global (shared) R2 value of 0.96 and a Ki of 450 nM. (B) Corresponding Lineweaver-Burk plot. These plots show decreasing Km and Vmax as the inhibitor concentration is increased consistent with uncompetitive inhibition.