Enzyme Inhibitors

• Enzyme activity can be prevented by enzyme inhibitors - molecules that bind to the enzyme that they inhibit. Inhibition can be competitive or non-competitive
• Competitive inhibitors: competitive inhibitor molecules have a similar shape to that of substrate molecules. They compete with the substrate molecules to bind to the active site, but no reaction takes place. Instead they block the active site, so no substrate molecule can fit in it
• If there is a high concentration of the inhibitor - it will take up nearly all of the active sites and hardly any of the substrate will get to the enzyme
• How much the enzyme is inhibited depends on the relative concentrations of the inhibitor and substrate
• If there is a higher concentration of substrate, then the substrate's chance of getting to an active site before the inhibitor increases - so increasing the concentration of substrate will increase the rate of reaction up to a point
• Non-competitive inhibitors: non-competitive inhibitor molecules bind to the enzyme away from its active site. This causes the active site to change shape so the substrate molecules can no longer bind to it
• Non-competitive inhibitor molecules don't compete with the substrate molecules to bind to the active site because they are a different shape. Increasing the concentration of substrate won't make any difference - enzyme activity will still be inhibited