🚫Enzyme inhibitors 🚫

• Inhibitors are molecues that prevent (or slow down) enzymes from carrying out their normal function of catalysis.
• Enzymes can be inactivated with inhibitors
• The two types of enzyme inhibition are competitive inhibition and non-competitive inhibition
• In competitive inhibition, a molecule or part of a molecule that has a similar shape to the substrate of an enzyme can fit into the active site of the enzyme. This blocks the substrate from entering the active site, preventing the enzyme from catalysing the reaction. The enzyme cannot carry out its function and is said to be inhibited. The non-substrate molecule is the inhibitor
• In competitive inhibition, substrate and inhibitor molecules present in a solution will compete with each other to bind to the active sites of the enzymes catalysing the reaction.
• The degree of inhibition in competitive competitive inhibition will depend on the relative concentrations of substrate, inhibitor, and enzyme.
• Most competitive inhibitors only bind temporarily to the active site of the enzyme so their effect is reversible. However, there are some exceptions such as aspirin
• A competitive inhibitor reduces the rate of reaction for a given concentration of substrate but does not change the Vmax. If the substrate concentration was increased enough there will be so much more substrate than inhibitor that the original Vmax can still be reached
• Statins are competitive inhibitors of an enzyme used in the synthesis of cholesterol. It helps reduce blood cholesterol concentration because high blood cholesterol levels can result in heart disease.
• Aspirin, a competitive inhibitor, irreversibly inhibits the active site of COX enzymes. This prevents the synthesis of prostaglandins and thromboxane. These chemicals are responsible for producing pain and fever.
• In non-competitive inhibition, the inhibitor binds to the enzyme at a location other than the active site. This alternative site is called the allosteric site. The binding of the inhibitor causes the tertiary structure of the enzyme to change so its active site changes. This results in the active site no longer having a complementary shape to the substrate of it is unable to bind to the enzyme. The enzyme cannot carry out its function and is said to inhibited. The inhibitor does not compete with the substrate for the active site
• Increasing the concentration of the enzyme or the substrate will not overcome the effect of a non-competitive inhibitor. Increasing the concentration of the inhibitor will decrease the rate of reaction further as more active sites will change shape.
• irreversible inhibitors cannot be removed from the part of the enzyme they are attached to.
• Organophosphates used as insecticides and herbicides irreversibly inhibit the enzyme acetyl cholinesterase which is necessary for nerve impulse transmission. This can lead to muscle cramps, paralysis, and even death if ingested.
• Proton pump inhibitors (PPIs), non-competitive inhibitors, are used to treat long term indigestion. They irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach, reducing the production excess acid which can lead to stomach ulcers if left untreated.
• End-product inhibition is a type of enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it. This serves as a negative feedback control mechanism for the reaction. Excess products are not made and resources are not wasted. It is an example of non-competitive reversible inhibition.