Stabilization of luciferase intermediates by fatty amines, amides, and nitriles

Long-chain aliphatic amides, mono- and diamines, mono- and dialcohols, and nitriles were found to inhibit the bacterial luciferase reaction by binding with an enzyme intermediate (II, the luciferase-bound 4 alpha-flavin hydroperoxide). Inhibition was determined by measuring the decay rates of the inhibitor-intermediate II complex at different inhibitor concentrations. The data fit a model which was used to estimate the KI. At high concentrations, a plot of the decay rate (k) vs 1/[I] produced a straight line; extrapolation of this to 1/[I] = 0 yields an estimate of the decay rate at infinite inhibitor concentration which we defined as the inhibitor-enzyme-substrate stabilization constant, kESI.