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What are Enzymes? – Roles, Examples, and Characteristics

Jul 7, 2022


The human body comprises different cells, tissues, and other complex organs. It releases some chemicals for the efficient functioning of biological functions like excretion, digestion, respiration, and a few other metabolic activities. These chemicals are generally termed enzymes. Therefore, they are essential for life as they govern all biological processes.

This article will provide you with solutions to the questions like what is an enzyme, what are their functions, what is their importance, their properties, and some others.


What are enzymes?

All biological reactions are catalysed by some special catalysts called enzymes. Therefore, they are defined as ‘biochemical catalysts.’ They enhance the rate of biochemical reactions, i.e., reactions in living organisms.

These are generally proteins that contain strings of amino acids. Their functioning is determined by their shape, sequence, and types of amino acids. They cause the reaction to occur even under unfavourable thermodynamic conditions.


The functions of cells rely on enzymes. These help in developing and speeding up the chemical reactions in cells. In short, they support cells to get things done. It can participate in biochemical reactions without destruction or irreversible modifications during the reaction. Therefore, they are considered biochemical catalysts.

The human body contains thousands of enzymes. It is evaluated that more than 75,000 enzymes are used in biofuel, brewing, dairy, and other manufacturing areas.


What is an enzyme’s role?

Their role is to reduce the activation energy, thereby allowing the reaction to occur at a lower temperature because of their reversible binding with reactants. The steps involved in the enzyme catalysis of a single reaction can be represented as given below:

E + S ⇌ ES* ⇌ ES ⇌ EX* ⇌ EP ⇌ EP* ⇌ P + E


Where S = Reactant (called Substrate),

P = Product,


ES and EP = Enzyme complexes,

EX* and EP* = Activated complexes at transitional state


The above reaction can be abbreviated as

E + S ⇌ ES ⇌ P + E


Where ES = Enzyme substrate complex.

In enzyme-catalysed reactions, though activation energy is lowered, the net energies of the reaction remain unchanged.

Examples of Enzymes

  1. Lipases: They are found in plants and the pancreas. They hydrolyse fat to fatty acids and glycerol.
  2. Amylase: These are found in animals and plants, particularly in saliva and pancreatic juices. It hydrolyzes amylum (starch) into maltose.
  3. Maltase: It occurs in yeast and hydrolyses maltose into glucose.
  4. Other enzymes: Renin is used to thicken milk to cheese; ligninase and cellulases help soften paper; catalase helps convert latex into rubber; lipases, proteases, and others are used in fabric softeners.

There are many more types of enzymes.

What are Enzymes Characteristics?

They have some remarkable properties. Some of them are given below:

  1. Specificity:

They are reaction specific, i.e., each catalyses only one chemical reaction. For instance, the enzyme urease can only hydrolyse urea to NH3 and CO2; it invertase hydrolysis sucrose to glucose and fructose; to hydrolyse maltose, the enzyme maltase is used.

  1. Efficiency:

Enzymes catalyse rates of biological processes at an extremely faster rate. A chemical reaction in the presence of enzymes proceeds hundreds to millions of times faster. Furthermore, these reactions occur at the body temperature and physiological pH range. They exhibit their activities even when they have been extracted from the source.

  1. Small Quantity:

A small number of enzymes can be highly efficient. It is because enzymes’ regeneration rate is very fast compared to chemical catalysts. For instance, a single molecule of enzyme carbonic anhydrase can decompose 36 million molecules of carbonic acid into CO2 and H2O in one minute.

  1. Optimum temperature and pH:

Each enzyme shows maximum activity at a certain temperature and pH, known as optimum temperature and pH. Under these conditions, most of the chemical reactions do not occur at appreciable rates if ordinary catalysts are used.

  1. Enzyme activators (coenzymes):

These are the substances that boost the enzyme activities in a reaction. For instance, if a protein contains a small amount of vitamin as the non-protein part, the activity of the protein is enhanced a lot. The activators are generally metal ions in a reaction.

  1. Enzyme inhibitors and poisons

Inhibitors or poisons are compounds that decrease the rate of enzyme catalysis reactions. They work by combining with the active functional group, thereby reducing or destroying their catalytic activity of them. Many drugs proceed in the human body because of their inhibiting nature.

Types of Enzymes

Every biological reaction requires a dissimilar kind of enzyme. As there is a large number of such biological reactions, hence, there is a large number of enzymes functioning in a living system. A certain cell, on average, contains about 3000 different kinds of enzymes. Each of them catalyses a different function and reaction.

According to the International Union of Biochemistry Classification, they are divided into six main types.

  1. Oxidoreductases:

These are responsible for vast energy-providing reactions of animals and plant tissues. During the reactions, the transfer of electrons and protons takes place, giving them oxidoreductase names.

  1. Transferases:

These are responsible for transferring atoms or groups of atoms from one substrate to another. For example, the enzyme transaminase catalyses the transfer of an amino group of one amino acid to the keto group of a keto acid.

  1. Hydrolases:

They bring hydrolysis of complex molecules to simple ones. For instance, lipase hydrolyses glycerides to glycerol and higher fatty acids. Some other hydrolase enzymes are peptidase, thiolase, phosphatases, etc.

  1. Lyases:

They catalyse the addition of groups to double bond or eliminate groups to create a double bond without undergoing oxidation, reduction, or hydrolysis process. For example, decarboxylase catalyses the removal of CO2, forming a carbonyl compound.

  1. Isomerases:

They catalyse the structural shifts present in a molecule. It brings a change in the shape of the molecule or the formation of isomers.

  1. Ligases:

The phosphate group of ATP is cleaved from ATP molecules. Also, linkages between groups are created in ligases catalysed reactions. These enzymes catalyse the ligation processes.

What are digestive enzymes and what do they do?

Digestion is the activity of using the nutrients from the food to give energy to the body, help it grow, and perform all vital functions. The proteins your body makes to break down food and aid digestion are naturally occurring digestive enzymes.

When you eat a meal or a munch, digestion undertakes in the mouth. The saliva in your mouth starts breaking down food immediately into a form the body can absorb. There are a lot of various points in the digestive process where enzymes are let go and triggered.

Your small intestine, stomach, and pancreas all make digestive enzymes. The pancreas is the real “powerhouse” of them. It produces the most crucial digestive enzymes, which help break down fats, proteins, and carbohydrates.

Types of Digestive Enzymes

There are numerous digestive enzymes. The chief digestive enzymes composed in the pancreas include –

  1. Amylase is present in the pancreas and mouth and breaks down composite carbohydrates.
  2. Lipase is present in the pancreas and breaks down fats.
  3. Protease is present in the pancreas and breaks down proteins.

Some other common enzymes in the small intestine are –

  1. Lactase breaks down lactose.
  2. Sucrase breaks down sucrose.


They are vital for biological processes. Without them, the life processes would be very slow and sluggish. For example, if there were no enzymes in the digestive system, it would take around 50 years to digest a single meal.

What an enzyme differs from a catalyst is in the sense that they catalyse the biological process and undergo change. Still, enzymes and catalysts are ultimately set free in the end. They can be used repeatedly and do not wear out or get used up.  

Frequently Asked Questions

1. What are some of the common enzyme-catalysed reactions?

A. As there are a lot of biochemical reactions that are catalysed by a different enzyme, there are a lot of common enzyme-catalysed reactions.

Inversion of cane sugarInvertaseYeast
Conversion of Glucose into Ethyl alcoholZymaseYeast
Decomposition of urea into NH3 and CO2UreaseSoybean
Conversion of proteins into peptides in the stomachPepsinStomach
Conversion of milk into curdLactic bacilliCurd

2. What are the industrial applications of enzymes?

A. Due to the availability and fast growth rate, they have a wide range of industrial applications. Industries like dairy, baking, beverage, animal feed, pulp and paper, polymer, detergent, leather, cosmetics, organic synthesis, and waste management highly use enzymes.

 3. How do enzymes act as catalysts?

A. Enzymes are highly specific in their actions. Each of them has a special region on its surface called the active site. The molecule the enzyme works with fits into this region. The molecule is called a substrate. The chemical reaction occurs at this active site, and the enzyme releases a new molecule or substance called the product.



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