Enzymes Functions | Definition | Classification

Enzymes Definition

 Kuhne in 1878 first used the term Enzyme. He described that enzymes are basically ‘Biological Catalysts’. In 1950 Sumner well-defined the Enzymes. Enzymes are Protein in nature that might be Simple or Combined Proteins interim as Specific Catalysts in the Biological Process. Enzymes are vital substances that improve the organism’s life in various ways. Enzymes Functions also described below:

Enzymes Functions

What are Enzymes Made of

Without any omission, all Enzymes are Proteins in Nature. Many Enzymes are Composed of Simple Proteins. These Enzymes are only composed of Amino Acid Molecules. But most of the Enzymes are composed of Conjugated Proteins. Enzymes Functions are very complex in nature.

Enzymes Functions


Enzymes composed of both Amino Acids molecules and Non-Protein parts. These Non-Proteins part of Enzymes are known as Coenzymes or Prosthetic Groups. If in the Enzymes Coenzyme or Prosthetic Group, is absent Enzyme is inactive.


In the Coenzyme, the protein part of the Enzyme is called as Apoenzyme.


The combination of Coenzyme and the Apoenzyme is known as Holoenzyme.

For example, Catalysis of Pyruvate to form Acetaldehyde is done by the Enzyme Pyruvate Decarboxylase. Enzyme Pyruvate Decarboxylase contains Thiamine Pyro Phosphate as non-protein part of the Enzyme without this Non-Protein part any Biological Reaction Cannot be processed. With the Apoenzyme the Non-Proteinaceous part is slackly or firmly attached.

Enzymes Functions

Enzymes Functions

Prosthetic Groups.

If the Non-Proteinaceous part or Coenzymes are firmly bound with the Apoenzymes than this is known as Prosthetic Groups. If the Non-Proteinaceous part or Coenzymes are loosely bound with the Apoenzymes than this is known as Coenzymes.

Enzymes Functions

Enzymes are Proteins

Enzymes are basically Proteins and Enzymes are fashioned by the living cells. Enzymes performance inside the body is as Biological Catalysts. Enzymes play a vital role in various processes like breathing, digestion, pumping of the heart, formation of body tissues, contraction of muscles, transport of ions across the plasma membranes etc.

During these Biological Processes Enzymes are itself catalyzed and boost up the Biochemical Reactions rate. In other words, we can also say that without there is no life without enzymes. But one it should be considered that Enzymes are inactive at Extreme Temperatures. At 0 Degree Centigrade Enzymes are Inactive and at 100 Degree Centigrade Enzymes are denatured. Enzymes work efficiently in Optimum Temperature. Enzymes Functions have diverse variety.

Types of Enzymes

Enzyme Commission of International Union of Biochemistry (IUB) in 1961 classified enzymes into the 6 major classes:

  1. Oxidoreductases
  2. Transferases
  3. Hydrolases
  4. Lyases
  5. Isomerases
  6. Ligases

Enzymes Functions


  1. Oxidoreductases

Oxidoreductases are those Enzymes which help in the Oxidoreduction Catalyzing reactions between Substrates A and B are known as Oxidoreductases

  1. Transferases

Transferases Enzymes are those which involve in the catalyzation process in such a way that they Transfer of (X) Group from one (AX )  Substrate to another (B) are recognized as Transferases.

On the basis of Group (X) Transferred, Transferases Enzymes are further divided into subclasses.

  • One carbon compounds
  • The Aldehyde or Ketonic Groups
  • Acyl groups
  • Glycosyl groups
  • Phosphate groups
  • Sulfur-containing groups
  1. Hydrolases

Hydrolases are such Enzymes which take part in Hydrolysis Reactions. These Enzymes are helpful in the direct addition of Water Molecule across the bond i.e. which in the end to be slashed. Hydrolases enzymes contain Esters, Ethers, Peptides and Glycosides as substrates.

  1. Lyases

Lyases are usually Enzymes reduced class. Lyases Enzymes involved in the Catalyzed elimination of an insignificant molecule from a Large molecule of Substrate. Lyases perform the Reversible Reactions also. It also involved in Catalysis Addition of small molecules into the Substrate Molecule.

The Lyases Enzymes are additionally Classified on basis of Linkage they attack:

  • C-C Bond
  • C-O Bond
  • C-N Bond
  • C-S Bond
  • C-Halide Bond
  1. Isomerases

Isomerases class Enzymes are composed of enzymes which help in the isomerization reactions. Isomerases help in forming Optical, Geometrical or Positional isomers.

  1. Ligases

Ligases Enzymes are also known as Synthetases. Ligases involved in catalysis process of synthesis reactions. These Enzymes are helpful in joining of Two molecules due to which Phosphate Bond of Adenosine Triphosphate (ATP) will break down. ATP breakage delivers vigor or energy for the Bond Formation. Ligases have following subclasses on the basis of Bond Formation:

  • C-O Bond
  • C-S Bond
  • C-N Bond
  • C-C Bond

Enzymes Functions

Lock and key model Vs Induced Fit Model

Enzymes Functions

Enzymes Function

Enzymes Functions are described below:

  1. Enzymes take part in the Catalysis Process of various Biological reactions
  2. Enzymes Boost up the Production Rate during the Metabolic Pathways.
  3. Various Blood Enzymes used as Investigative Indicators of numerous diseases.
  4. If in the Blood Transaminases level is raised it acts as an Indicator of Jaundice that’s basically a disorder of Liver.
  5. Many Enzymes are utilized for Beneficially Medicinal purposes.
  6. Penicillinase is notorious enzyme used for the treatment of Allergic Reactions to Penicillin
  7. Enzyme Asparaginase is used for the treatment of Leukemia.
  8. While Diastase is the Enzyme used for the treatment of Indigestion.

Enzymes Examples

  • Lipases

These are the  Enzymes which take part in the Fats Digestion inside the Gut.

  • Amylase

Amylase is found in saliva. These Enzymes take part in the process of changing Starches into Sugars.

  • Maltase

These enzymes are present in Saliva. They involved in the Break down of the Maltose Sugar into Glucose Sugar. Sugar Maltose is abundantly present found in  Potatoes, Pasta, and Beer.

  • Trypsin

Trypsin enzymes are abundantly present in the small Intestine. They help in the breakdown of  Proteins into simple Amino Acids molecules.

  • Lactase

These enzymes are also present in the small intestine. They help in break down of Lactose into glucose and galactose.

  • Acetylcholinesterase

These Enzymes involved in the breakage of the Neurotransmitter Acetylcholine in Nerves and Muscles.

  • Helicase 

Helicase Enzymes help in the unraveling of the DNA.

  • DNA Polymerase

DNA Polymerase helps in the DNA Synthesis from Deoxyribonucleotides.

Enzymes Functions