While uncompetitive inhibition requires that an enzyme-substrate complex must be formed, non-competitive inhibition can occur with or without the substrate present.
This reduction in the effective concentration of the E-S complex increases the enzyme's apparent affinity for the substrate through Le Chatelier's principle (Km is lowered) and decreases the maximum enzyme activity (Vmax), as it takes longer for the substrate or product to leave the active site. Uncompetitive inhibition works best when substrate concentration is high. An uncompetitive inhibitor need not resemble the substrate of the reaction it is inhibiting.
The Lineweaver–Burk equation states that:
The Lineweaver–Burk plot for an uncompetitive inhibitor produces a line parallel to the original enzyme-substrate plot, but with a higher y-intercept, due to the presence of an inhibition term :
Notes and references
- Cleland, W. W. (1963). "The kinetics of enzyme-catalyzed reactions with two or more substrates or products". Biochimica et Biophysica Acta (BBA) - Specialized Section on Enzymological Subjects. 67: 173–187. doi:10.1016/0926-6569(63)90226-8. PMID 14021668.
- Rhodes, David. "Enzyme Kinetics - Single Substrate, Uncompetitive Inhibition, Lineweaver-Burk Plot". Purdue University. Retrieved 31 August 2013.
- Cornish-Bowden, A. (1974). "A simple graphical method for determining the inhibition constants of mixed, uncompetitive and non-competitive inhibitors". The Biochemical Journal. 137 (1): 143–144. doi:10.1042/bj1370143. PMC 1166095. PMID 4206907.