Enzymes | Definition, Classification & Functions

By | July 24, 2019

Enzymes Definition

Enzymes Definition and Function: Kuhne in 1878 first used the term Enzyme. He described that enzyme is basically ‘Biological Catalysts’. In 1950 Sumner well-defined the Enzyme. The enzyme is Protein in nature that might be Simple or Combined Proteins interim as Specific Catalysts in the Biological Process. An enzyme is a vital substance that improves the organism’s life in various ways.


What are Enzymes Made of:

Enzymes are molded from Amino Acids, due to this, they are protein in nature. An enzyme is formed, by stringing 100 to 1,000 Amino Acids. Are Enzymes reusable ? is a very arousing question nowadays. Without any omission, all Enzymes are Proteins in Nature. An enzyme is Composed of Simple Proteins. These are only composed of Amino Acid Molecules. But most of the Enzymes are composed of Conjugated Proteins. Enzymes Functions are very complex in nature.



Enzyme composed of both Amino Acids molecules and Non-Protein parts. These Non-Proteins part of Enzyme is known as Coenzymes or Prosthetic Groups. If in the Enzyme 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.


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 are Proteins

Enzymes Biology: Enzymes are basically Proteins and Enzymes are fashioned by the living cells. Enzyme performance inside the body is as Biological Catalysts. The enzyme plays 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, Enzymeitself catalyzed and boost up the Biochemical Reactions rate. In other words, we can also say there is no life without enzyme. But one it should be considered that Enzyme is inactive at Extreme Temperatures. At 0 Degree Centigrade Enzyme is Inactive and at 100 Degree Centigrade Enzymes are denatured. The enzyme works efficiently in Optimum Temperature. 

Properties of Enzymes

Enzymes properties are described below:

  • Enzymes are made up of amino acids; they can create active sites with a variety of properties that can specify into different substrates.
  • Enzymes are basically multifaceted macromolecules compounds which comprised of high molecular weight.
  • They help to catalyze biological chemical reactions inside a cell.
  • They aid in the breakdown of bulky molecules into minor molecules or sometimes fetch two minor molecules to create a bigger fragment. This process is known as Biocatalysts.
  • Enzymes do not help in the initiation of the chemical reaction. Yet, they aid in quickening the biochemical reaction.
  • Enzymes distress the amount of biological reaction while not the direction of the reaction.
  • Various Enzymes comprised of high variety.
  • Enzymes are precise in accomplishment.
  • Enzymatic action declines with raising in temperature.
  • They express supreme activity at a pH of 6-8 optimum condition.
  • Rate of reaction increased with the increase in substrate concentration.
  • All enzymes are basically proteins in nature but enzymes are not protein.
  • Ribozymes are basically Nucleic Acids (RNA) in nature which act as enzymes.
  • Active sites of enzymes have tertiary protein structures which have cracks or Pockets which are known as Active Site inside which substrate spasms.
  • Enzymatic Catalysts work efficiently at High Temperature and Pressure. But at high temperature (> 40°C) enzymes become damaged or denatured.
  • Polar molecules attract other polar molecules. The non-polar molecules attract the non-polar molecules. That’s means that every part of the active site can attract or repel other molecules to create a good match.
  • Size and shapes of active site can be created by the specific molecules to better fit.
  • When the active site comes near to ions, opposite charges attract each other, while two similar charges repel each other and vice versa. That’s another way in which active sites attract different charges and repel similar charges to create a perfect match.

What Is A Substrate in Biology?

Substrate Definition in Biology

Substrate Biology: An enzyme is a molecule which works as a biological catalyst which speeds up the rate of a chemical reaction. In living organisms, the enzyme acts on many substances. Substrates are a substance or surface which is acted by an enzyme. Substrates are transmitted into the active site of the enzyme. When enzyme substrates are formed, for its reaction enzyme exert force on the substrates, and in the result, the product does the reaction.

The substrates and enzyme form a bond, which is cause to change conformation and shape in the enzyme. In the result, the shape is formed that how much pressure on substrates applied by enzyme, either force applied on molecules together or taking it apart. In our body, almost all molecule work as a substrate for different functions. Because for perform different functions or done works, our body requires a large amount of energy and time, and reactions take a specific enzyme to works along. Once a reaction acts, the substrates become different chemically and called a Product.

Active Site Definition Biology:

Active Site Definition: Enzymes catalyze many chemical reactions; include the string of nucleotides together and amino acid in DNA, proteins, the breakdown of sugar and fat into energy. Without the enzyme, life does not exist.

The active site of the enzyme is the site on which the enzyme binds to substrate and increase the reaction chances. It is the specific region of an enzyme where catalysis process takes place or where a chemical reaction takes place. The active site is made of residues at the binding site. The enzyme will have only one active site which will fit with only one substrate.


Enzymes Classification

Classification of Enzymes are described below:

 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

Types of Enzymes:



  1. Oxidoreductases

Oxidoreductases is Enzyme which helps in the Oxidoreduction Catalyzing reactions between Substrates A and B are known as Oxidoreductases

  1. Transferases

Transferases Enzyme involves 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 Enzyme is further divided into subclasses.

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

Hydrolases is Enzyme which takes 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 enzyme contain Esters, Ethers, Peptides and Glycosides as substrates.

  1. Lyases

Lyases are usually Enzyme reduced class. Lyases Enzyme 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 Enzyme is additionally Classified on the basis of Linkage they attack:

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

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

  1. Ligases

Ligases Enzyme 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


Lock and key model Vs Induced Fit Model


Enzymes Function

Enzymes Functions are described below:

  1. Enzyme take part in the Catalysis Process of various Biological reactions
  2. Enzyme 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.

How do enzymes work:

Enzyme React with the substrate and form products in the following manner:


Enzyme chemically recognizes, bind and modify substrates.

Enzymes Examples

  • Lipases

It takes part in the Fats Digestion inside the Gut.

  • Amylase

Amylase is found in saliva. It takes part in the process of changing Starches into Sugars.

  • Maltase

This enzyme is 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 enzyme is abundantly present in the Small Intestine. They help in the breakdown of  Proteins into simple Amino Acids molecules.

  • Lactase

It is also present in the small intestine. They help in break down of Lactose into glucose and galactose.

  • Acetylcholinesterase

Acetylcholinesterase Enzyme involved in the breakage of the Neurotransmitter Acetylcholine in Nerves and Muscles.

  • Helicase 

Helicase Enzyme help in the unraveling of the DNA.

  • DNA Polymerase

DNA Polymerase helps in the DNA Synthesis from Deoxyribonucleotides.


React Jest

Enzymes Substrate Complex:

In an active site, when a substrate attached to an enzyme then an intermediate is formed, is called an enzyme-substrate complex. Every enzyme has to need a specific substrate to perform catalyze the process. When the enzyme performs catalyze the process, the substrate binds to the active site. By this reaction active site changes its shape a bit for a better fit of an enzyme. Then, enzyme substrates complexes are formed. Enzyme substrates complex forms when the bonds are unstable. Because of it a temporary bond between the enzyme and its substrates.


What Is Induced Fit Model:

The induced-fit model described below: