Article for students on Enzymes

Type of Enzymes

Enzymes are proteins produced by living organisms to carry certain metabolic, functional specific biochemical reactions in the body. They are biological catalysts (biocatalysts) that facilitate the reaction process inside the body at an amazingly high rate. The acceleration of a reaction consequence of a decrease in the activation energy, altering the reaction pathway or following specific reaction dynamics in the body. Enzymes (E) allow reactions to proceed at the fastest rates in the mild conditions of temperature, pH, and pressure of the cells.1

Enzymes are a linear chain of amino acids, actually made up of 1000s of amino acids, which form a three-dimensional structure. The variation in linking in a specific way gives different enzymes. The enzyme chains fold all over to create unique shapes, and these shapes provide the enzyme with characteristic chemical potential. Most enzymes also contain a non-protein component known as the co-factor. Substrates (S) are the substances on which enzymes act. A reacting substrate binds to the activation site of an enzyme forming an S-E complex, and the reaction occurs, then generated product(s) (P) liberated from the active site.2

Figure 1: alpha-amylase-enzyme

Enzyme nomenclature is derived from the substrates that are catalyzed or by the reaction itself. Usually, “-ase” is added as a suffix. According to the International Union of Biochemistry, enzymes differentiate with letters and numbers- the letters EC with four numbers representing the four elements. The first number represents enzymes classified according to the mechanism of the enzymatic reaction. Enzymes categorize as per the type of catalytic reactions. The seven types of enzymes are hydrolases, oxidoreductases, lyases, transferases, ligases, isomerases, and translocases. Some enzymes are ribonucleic acid (RNA) molecules (ribozymes).2,3

Types

Function

Hydrolases

Hydrolases are hydrolytic enzymes. These enzymes catalyze reactions that involve the process of hydrolysis. They cleave single bonds by adding water. Some hydrolases function as digestive enzymes to break the peptide bonds in the proteins.

Oxidoreductases

The enzyme catalyzes oxidation-reduction reactions where the electrons tend to travel from one molecule to the other. And electron transfers in the form of hydride ions or a hydrogen atoms.

Lyases

These enzymes catalyze reactions where functional groups are added to break double bonds in molecules or bonds formed by the removal of functional groups. Adds water, carbon dioxide, or ammonia across double bonds or eliminates these to create double bonds.

Transferases

These enzymes catalyze reactions where the functional groups insert and break double bonds in molecules or bonds formed by removing functional groups. Add water, carbon dioxide, or ammonia across double bonds or eliminates these to create double bonds.

Ligases

The Ligases enzymes are known to charge the catalysis of a ligation process. Ligases form bonds by the removal of the water component.

Isomerases

The Isomerases enzymes catalyze the structural shifts present in a molecule, causing the change in the shape of a molecule. These enzymes catalyze the reactions where a functional group is moved to another position within the same molecule resulting in an isomer of the earlier molecule.

Translocases

These enzymes catalyze the reaction of ions or molecules moving across a membrane or separating within the membranes.

Figure 2: Schematics of an enzymatic reaction1

Reference:

1. Blanco, A., & Blanco, G. (2017). Enzymes. Medical Biochemistry, 153–175. https://doi.org/10.1016/b978-0-12-803550-4.00008-2

2. Berg, J. M., Tymoczko, J. L., Stryer, L.(2002). Chapter 8. Enzymes: Basic Concepts and Kinetics

3. International Union of Biochemistry, The Enzyme Database. https://www.enzyme-database.org/class.php