Enzymes accelerate reactions by reducing the activation energy of the substrate - the energy necessary to bring the molecules into an active state. Enzymes deform the electron shells of substrates, thereby facilitating the interaction between them. At the first stage of enzymatic catalysis, the formation of an enzyme-substrate complex occurs, where the enzyme and substrate can be connected by ionic, covalent, or other bonds. The formation of the E-S complex occurs almost instantly. During the second stage, the enzyme changes the substrate that becomes more accessible for the corresponding chemical reaction. This stage determines the speed of the whole process. At these stages of enzymatic catalysis, repeated changes in the tertiary structure of the enzyme occur. This process leads to a specific spatial orientation of active groups of the enzyme with the substrate. These active groups interact with each other at various stages of substrate transformation. Next, a chemical reaction occurs and a complex between a product of the reaction and the enzyme is formed. The final process is associated with the release of the product of reaction from the complex.