Many drugs work as enzyme inhibitors. An inhibitor is a molecule that binds to an enzyme and stops it catalysing its reaction.A drug that acts as an inhibitor often has a shape similar to the substrate, so it fits into the active site. It binds there through the same kinds of interaction as the substrate (hydrogen bonds, ionic interactions, van der Waals forces), but it does not react. While it occupies the active site, the substrate cannot bind, so the reaction is blocked.
The more strongly the drug binds, and the higher its concentration compared with the substrate, the more effective the inhibition. Some inhibitors bind so strongly, sometimes by forming a covalent bond, that the enzyme is permanently inactivated.Because active sites are stereospecific, often only one enantiomer of a chiral drug fits. The other enantiomer may be inactive or have different effects, which is why many drugs are made as a single enantiomer.Designing drugs. Once the 3D shape of an enzyme's active site is known, chemists can use computer modelling to design molecules that fit it and bind to it strongly. Computers can test thousands of possible structures quickly, so fewer compounds need to be made and tested in the laboratory, saving time and money.Example. Penicillin inhibits an enzyme that bacteria use to build their cell walls. It binds in the active site, the bacteria cannot make strong walls, and they burst.
The more strongly the drug binds, and the higher its concentration compared with the substrate, the more effective the inhibition. Some inhibitors bind so strongly, sometimes by forming a covalent bond, that the enzyme is permanently inactivated.Because active sites are stereospecific, often only one enantiomer of a chiral drug fits. The other enantiomer may be inactive or have different effects, which is why many drugs are made as a single enantiomer.Designing drugs. Once the 3D shape of an enzyme's active site is known, chemists can use computer modelling to design molecules that fit it and bind to it strongly. Computers can test thousands of possible structures quickly, so fewer compounds need to be made and tested in the laboratory, saving time and money.Example. Penicillin inhibits an enzyme that bacteria use to build their cell walls. It binds in the active site, the bacteria cannot make strong walls, and they burst.