Drug- Target Interaction as Enzymes
- Macromolecules of biological origin perform various functions in the body.
- For example, proteins which perform the role of biological catalysts in the body are called enzymes.
- They are crucial to communication system in the body are called receptors.
- Carrier proteins carry polar molecules across the cell membrane.
- Nucleic acids have coded genetic information for the cell. Lipids and carbohydrates are structural parts of the cell membrane.
- Catalytic Action of Enzymes
- In order to carry catalytic activity enzymes perform 2 major functions:
- The first function of an enzyme is to hold the substrate for a chemical reaction. Active sites of enzymes hold the substrate molecule in a suitable position, so that it can be attacked by the reagent effectively.
Substrates bind to the active site of the enzyme through a variety of interactions such as ionic bonding, hydrogen bonding, van der Waals interaction or dipole-dipole interaction.
- The second function of an enzyme is to provide functional groups that will attack the substrate and carry out chemical reaction.
- Drug-Enzyme Interaction
- These drugs can block the binding site of the enzyme and prevent the binding of substrate, or can inhibit the catalytic activity of the enzyme. Such drugs are called enzyme inhibitors.
- Drugs inhibit the attachment of substrate on active site of enzymes in two different ways;
- Drugs compete with the natural substrate for their attachment on the active sites of enzymes. Such drugs are called competitive inhibitors.
- Some drugs do not bind to the enzyme’s active site. These bind to a different site of enzyme which is called allosteric site. This binding of inhibitor at allosteric site changes the shape of the active site in such a way that substrate cannot recognise it.
- If the bond formed between an enzyme and an inhibitor is a strong covalent bond and cannot be broken easily, then the enzyme is blocked permanently.
- The body then degrades the enzyme-inhibitor complex and synthesises the new enzyme.