=Enzyme Inhibitors= An enzyme inhibitor is a molecule that binds to an enzyme and decreases its activity. ==Competitive Inhibitors== [image:http://i.imgur.com/PKAD3hz.png?2] A competitive inhibitor binds reversibly to the enzyme active site. This prevents any substrate from binding to the enzyme. Less enzyme-substrate complexes are formed slowing down the reaction rate. Competitive inhibition can be overcome by increasing the substrate concentration. Because the inhibitor and substrate are in competition for the active site, increasing substrate concentration increases the likelihood that that substrate will bind and the reaction will progress normally. ==Non-Competitive Inhibitors== [image:http://i.imgur.com/xP2Pw7m.png?1] A non-competitive inhibitor does not bind to the active site, instead it binds to a regulatory region sometimes referred to as a allosteric site. When a non-competitive inhibitor binds to an enzyme it causes it to change shape (a conformational change). The structure of the active site is altered and the substrate will no longer fit into the active site. As a result no enzyme-substrate complex is formed slowing down the reaction rate. Because the inhibitor does not compete for the active site, increasing the substrate concentration has no affect on enzyme activity. ==Reversible & Irreversible== Inhibitor binding is either reversible or irreversible. Irreversible inhibitors usually react with the enzyme and change it chemically (e.g. via covalent bond formation). These inhibitors modify key amino acid residues needed for enzymatic activity. In contrast, reversible inhibitors bind non-covalently. ==Application== Enzyme inhibitors can be used as herbicide and pesticides, to kill pathogens, to treat metabolic imbalances Many drug molecules are enzyme inhibitors, so their discovery and improvement is an active area of research in biochemistry and pharmacology.