Inhibition Kinetics of the Monolignol Biosynthetic Enzymes

To derive the inhibition constants K_ic, K_iu and K_is, we obtained K’_m and V’_max, the apparent K_m and V_max of the inhibited enzyme at each inhibitor concentration, and plotted K’_m/V’_max against the inhibitor concentration [I] and 1/V’_max against [I] according to Equations 2 to 4 (below). For evaluating inhibition kinetics, different concentrations of inhibitors were added to the assays. Reaction rates were analyzed by Lineweaver-Burke plots to determine the modes of inhibition. If the addition of inhibitor increases the K_m, the mode of inhibition is competitive, meaning that the inhibitor and the substrate both bind to the same active site in a competitive manner. If V_max decreases as the inhibitor is added, the inhibition is non-competitive, meaning that the inhibitor binds to an alternative regulatory site on the enzyme. If a high concentration of substrates reduces the V_max, the reaction is said to have substrate self-inhibition, that is, multiple substrate molecules can bind to an enzyme forming an inactive complex. Mixed inhibition is when multiple modes of inhibition (competitive, uncompetitive and substrate) are observed. Click here (Materials and Methods). If you have any questions about these data, would like to use these data for publication, or would like to collaborate, please contact Vincent Chiang Click here (Contacts Page).

Last Updated: April 12, 2015

Competitive inhibition equation

Un-competitive inhibition equation

Substrate self-inhibition equation