Enzymes are special proteins in our bodies that help speed up chemical reactions. They act like tiny workers, breaking down large molecules into smaller ones or joining smaller molecules together. Enzymes have specific jobs and are like keys that fit into locksβ€”each enzyme works with a particular molecule, called a substrate. They make the reactions happen faster by lowering the energy needed for the reaction to occur. Enzymes are crucial for digestion, energy production, and many other processes in our bodies. They are like the superheroes of our cells, making sure everything runs smoothly.

Major classes of enzymes

Classes of enzymes


These enzymes catalyze oxidation-reduction reactions, involving the transfer of electrons between molecules. Examples include dehydrogenases, oxidases, and reductases.


Transferases facilitate the transfer of functional groups, such as methyl, phosphate, or glycosyl groups, from one molecule to another. Examples include kinases, transaminases, and glycosyltransferases.


Hydrolases catalyze hydrolysis reactions, where water is used to break chemical bonds. They help in the breakdown of larger molecules into smaller units. Examples include lipases, proteases, and nucleases.


Lyases catalyze the removal of groups from or addition of groups to substrates, resulting in the formation of double bonds. Examples include decarboxylases, synthases, and deaminases.


Isomerases facilitate the rearrangement of atoms within a molecule, resulting in the formation of isomers (molecules with the same molecular formula but different structural arrangements). Examples include racemases, mutases, and epimerases.


Ligases catalyze the joining of two molecules by utilizing ATP as an energy source. They are involved in the synthesis of larger molecules, such as DNA, RNA, and proteins. Examples include DNA ligase and RNA ligase.

Enzyme Action

Enzymes function by binding to specific molecules called substrates and converting them into products. The enzyme-substrate complex forms when the enzyme’s active site (a region with a specific shape and chemical properties) interacts with the substrate. The enzyme then catalyzes the conversion of the substrate into the product(s).

Enzymes actions

Substrate Binding

The substrate molecules bind to the active site of the enzyme through a process known as the “lock and key” or “induced fit” model. The active site’s specific shape and chemical properties allow it to bind only with the complementary substrate.


Once the substrate is bound to the enzyme, catalysis occurs. Enzymes can lower the activation energy required for a reaction, enabling it to proceed more rapidly. They achieve this by stabilizing the transition state of the reaction, promoting the formation of the product.

Product Formation

The catalyzed reaction leads to the conversion of the substrate(s) into product(s). The products have a different chemical structure than the substrates.

Release of Products

After the reaction, the enzyme releases the products, allowing it to bind to other substrates and continue the catalytic cycle. The enzyme itself remains unchanged and can be reused multiple times.

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