Enzyme-substrate Complexes

• Enzyme-substrate complexes are integral to the process of enzymatic reactions. As biological catalysts, enzymes speed up chemical reactions in our bodies.
• Enzymes usually interact with very specific substrates which are the molecules an enzyme acts upon during a biochemical reaction. This is known as the ‘lock and key’ theory.
• For an enzyme-substrate complex to form, the enzyme and substrate must collide with enough energy. This ensures successful binding and triggers the chemical reaction.
• The part of the enzyme where the substrate molecule fits and binds is known as the active site. It has a unique shape that is complementary to the shape of the substrate.
• Enzyme-substrate complex formation helps lower the activation energy of a reaction. This is the energy needed for a reaction to occur and lowering it speeds up the reaction.
• After the enzyme-substrate complex is formed, the enzyme will catalyse the reaction, allowing the substrate to be converted into product(s). This can be breaking down substrates into smaller molecules or combining substrates to form a large molecule.
• Once the reaction has taken place, the enzyme-product complex is formed. The products are released because they no longer fit into the active site of the enzyme. The enzyme is then free to repeat the process with other substrate molecules, as it has not been consumed in the reaction.
• Understanding the formation and function of enzyme-substrate complexes is crucial in appreciation of metabolism, digestion and numerous other biological processes.
• Factors such as temperature, pH and substrate concentration can affect the rate at which the enzyme-substrate complex is formed. If the conditions are vastly different from what the enzyme is adapted to, the active site may change shape (denature) and the enzyme will no longer be able to catalyse reactions.