Various types of enzymes

Enzymes are colloidal, thermolabile bio-catalysts, synthesized by the living cells (both animal and plant cells and also including the microorganism) which are protein in nature, and do specific reactions. The enzymes do all the metabolic reaction in our body and plays a vital role in energy production. There are various types of enzymes which play different roles in our body. A particular enzyme acts for a particular substrate. Enzyme and substrate complex form by lock and key mechanism.

Working mechanism of various types of enzymes in metabolic reaction.
Working mechanism of various types of enzymes in metabolic reaction.

HISTORICAL BACKGROUND: Berzelius in 1836 coined the term ‘Catalysis’. In 1878, a German physiologist Wilhelm Kuhne used the word ‘Enzyme’ to indicates the biocatalysts.

TYPES OF ENZYMES: There are various types of enzymes. Firstly, the enzymes are classified into two broad categories- a. Intracellular enzymes, which become functional only within the cell, where they are synthesized, b. Extracellular enzyme, which are active outside the cell. All the digestive enzymes are belonging in the second category.

By International Union Of Biochemistry (IUB) the enzymes are divided into six major classes according to their nature of reaction. These six classes are following:

OXIDOREDUCTASES: These are the enzymes which are involved in oxidation-reduction reaction. They transfer oxygen and hydrogen atom or electron from one substance to another. A-H+B = A+B-H (reduction reaction where B is reduced), A+O = AO (A is oxidized). Example: Lactate dehydrogenase, Oxidase.

  • TRANSFERASES: The enzymes that catalyses the transfer of functional groups (may be methyl, acyl, phosphate etc) from one substance to another. A-X + B = A + B-X. Example: Kinase enzymes (transfer phosphate group), Transaminase, Nucleoside monophosphate.
  • HYDROLASES: Enzymes that bring about of various compound and catalyze the formation of two product from a substrate by hydrolysis, known as hydrolase enzyme. AB+H2O=AH+B2O. Example: Chymotrypsin, Lipase, Amylase, Pepsin etc.
  • LYASES: Enzymes, catalyse non-hydrolytic addition and removal of water, ammonia carbon dioxide from a substrate. In this reaction C-C, C-N, C-O, C-S bonds may be cleaved. AB+XY=AX+BY. Example: Fumarase, Decarboxylase, Aldolase etc.
  • ISOMARASES: These enzymes involved in all isomerization reactions. It helps in intermolecular rearrangement and form isomers. As example A is an isomer of A’ and the reaction is catalysed by an isomerase enzyme. Example: Mutase, Triose phosphate isomerase.
  • LIGASES: These enzymes catalysing the synthetic reactions. It joins two molecules together to synthesis of new C-C, C-O, C-S bond by using the ATP. It is also known as ligation reaction. A+B=A-B, where A and B molecules are joint together by using ATP and form A-B compound. This reaction is catalysed by the ligase enzyme. Example: Glutamine synthetase, Amino acyl tRNA synthetase etc.

FUNCTION OF ENZYMES: As enzymes are known as biocatalyst it plays a vital role in the biochemical reaction inside the body of an organism. It accelerates the speed of the reactions. Some enzymes such as Pepsin, Trypsin, Lipase etc, help in digestion and do other metabolic reactions of our body. Enzymes also helps to protect our body from various diseases by digesting the pathogens entering into the body. Some enzymes like acrosomal enzymes participates in fertilization. Oestrogens, Progesterone, Testosterone etc, has an important role in reproduction. There are also many other enzymes which serve a wide range of important functions in our body and help us to be alive.

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