How does an enzyme performs catalystic activity with substrate molecule?
Answers
Enzymes are specific to their substrates and their specificity is determined by the active site.Enzymes can perform catalytic activity with a substrate molecule by two methods:
Lock and Key hypothesis: This hypothesis was put forth by Emil Fischer in 1894. Enzyme has a special site called as active site. the conformation of this active site corresponds to the shape of the substrate which fits into the active site. Enzyme is the lock and substrate is the key. A particular substrate can only fit into active site of the enzyme to form the enzyme substrate complex. (ES complex) This intermediate complex is later broken to form enzyme and the products. Enzyme undergoes no change but helps in forwarding the reaction. This is called as lock and key hypothesis.
Induced fit hypothesis: Daniel Koshland introduced Induced fit hypothesis.According to this hypothesis the substrate is not the exact fit for the enzyme’s active site, but as the substrate approaches the active site, the active site alters it shape slightly to fuse with the substrate.
Induced fit indicates a continuous change in the conformation and shape of an enzyme in response to substrate binding. This makes the enzyme catalytic which results in the lowering of the activation energy barrier causing an increase in the overall rate of the reaction. In other words, when a substrate binds to an enzyme, it will change the conformation of the enzyme. This forms a transitional intermediate which lowers the activation energy and allows the reactants to proceed towards the product at a faster rate. In the case of macromolecules (e.g. proteins), induced fit shows the changes in the shape of a macromolecule in response to a ligand binding so that the binding site of macromolecule conforms more efficiently to the shape of the ligand. The enzyme will change its shape until it is completely complementary to a substrate to activate the enzyme-substrate complex.
Enzymes are specific to their substrates and their specificity is determined by the active site.Enzymes can perform catalytic activity with a substrate molecule by two methods: ... Enzyme has a special site called as active site.