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The term enzyme was given by FW. Kuhne (1878). They are generally made up of proteins and catalyze biochemical reactions. They are specific and have three-dimensional structure with highly specific one or more active sites for the recognition of substrates. The active site (lock) of the enzyme binds with its substrate (key) as “lock and key model”, given by Fisher (1890) (Fig. 16.1).

Fig. 16.1 Mechanism of enzyme action.

Some enzymes also have non-protein parts, called prosthetic groups, that can be inorganic (cofactor, e.g. nitrogenase having Mo, hydrogenase having Ni, catalase having Fe2+, etc.) or organic (coenzymes, e.g. coenzyme A) molecules. Some RNA molecules, called ribozymes, also have catalytic function reported by Cech (1986), which catalyze either their own cleavage or cleavage of other RNA and DNA molecules. Some antibodies, called abzymes, not found naturally, have also been reported to have catalytic activities, e.g. monoclonal antibodies.

Enzymes, required in very low amount, increase the rate of reaction by 103-106 times by lowering the activation energy. They do not take part in the reaction and operate under mild conditions of temperature, pH, pressure, etc. Carbonic anhydrase, catalyzing the reaction:

CO2 + H2O          —-         H2CO3

is the fastest enzyme enhancing 107 times reaction rate in comparison to the un catalyzed reaction.

The first isolated and crystallized enzyme was urease (J. Sumner, 1926), and insulin was the fi enzyme of which the amino acid sequence was given by Sanger (1953).

Enzyme technology utilizes purified enzymes for generating useful products and service e.g., industrial processes, medicine, research (e.g. Taq DNA polymerase obtained from thermophilic bacterium, Thermus aquaticus, used in PCR), recombinant DNA technology, etc. Though, purified enzymes are costly but they do not produce any unwanted byproducts, thus, the purification of the product becomes easier. Most of the enzymes are used in food and detergent industries. Sometimes, the byproducts produced by whole cells add to the quality of the product, e.g. wine and beer. Most of the enzymes are obtained from microorganisms (e.g. amylase from the bacterium Bacillus fungus Aspergillus, rennet from the fungus Mucor miehei) as it is easier to grow them in fermenters and manipulate them genetically. Some enzymes are obtained from higher plants (e.g. papain from papaya latex, amylase from malted barley) and animals (e.g. rennet containing chymosin enzyme from the pancreas of calf) also.

Enzymes are used since ancient times, e.g. for bread, cheese, wine and beer making, etc. In 1950s purified enzymes are either used in freely suspended form or in immobilized form, where the enzymes are fixed to some suitable inert carrier material, e.g. agarose, calcium alginate, polyacrylamide, carbon, clay, membrane, etc. When enzymes are used in immobilized form, the

separation of enzyme from the product becomes easier and the immobilized enzyme can be used
repeatedly. But sometimes, immobilization of the enzymes results in the loss of activity due to immobilization in a wrong orientation (e.g. involvement of active site in immobilization) and, thus, increase in.

Enzymes are used since ancient times, e.g. bread, wine and beer, etc. Some of the mod applications of the purified enzymes in various industries are:

1. Food and Brewing Industry

(i) Amylase from the fungus catalyses the breakdown of starch into simple sugars in dough in bakery for the production of bread, buns, etc. Simple sugars are used by the yeast to generate CO2 that gets entrapped to raise the dough. Amylase is also used in brewing for the conversion of starchy material to simple sugars that are utilized by yeast for beer (ethanol) production under anaerobic conditions.

Amylases are also used to convert starch into glucose and various syrups.

(ii)  Proteases also help in bakery and brewing for the conversion of complex proteins to simpler short peptides and amino acids.

(iii) Chymosin, which is a protease (in rennet), is used in dairy industry for cheese production to coagulate protein casein in milk.

(iv) Lipases are used to enhance ripening or cheese

(v) Cellulose is used in the production of fruit juices for the removal of cellulose impurities.

(vi) Glucose isomerase is used to convert glucose into fructose syrup that is used in soft drinks.

(vii) Invertase is used in chocolates where the centre of chocolates is filled with sucrose and the enzyme invertase. After some time, sucrose gets converted into invert sugar (glucose + fructose), which being more soluble and sweeter than sucrose, makes the centre of the chocolate soft and sweet.

2. Detergent Industry

i.Amylase (from Bacillus, Aspergillus niger) is used to remove resistant stains of starch residues with dirt on the cloths.

ii. Proteases (from Bacillus, Clostridium) are used to remove proteinaceous spots of milk, blood, etc. in association with ditto They cause allergic reactions, therefore, the protease granules are encapsulated in soluble wax coating.

iii. Lipases from Bacillus to remove oily spots on clothes.

iv. Cellulases from fungi are used for digesting away small fibres raised from the cotton fabric (made up of cellulose) with associated soil particles without damaging the major fibres.

3. Medical and Pharmaceutical Field

 i. Amylase, lipase, proteases, papain are used to cure digestive disorders due to starch, oil and proteins, respectively.

ii. Trypsin is used to dissolve blood clots.

iii. Many enzymes are used in disease diagnosis tools, e.g. ELISA, diabetes diagnosis kit that utilizes the enzymes glucose oxidase and peroxidase to detect the presence and quantity of glucose in blood and urine, various biosensors, etc.

iv. Lysozyme obtained from hen’s egg albumin (egg white) digests away bacterial cell wall and is used as antibiotic.

v. Lactase (from Kluyveromyces lactis, Aspergillus niger) treated milk is safely used by those people who are sensitive to lactose as their digestive system does not produce lactase enzyme and, thus, they cannot digest lactose of milk.

4. Leather Industry

Protease from pancreas is used to remove hair from hides.

5. Textile and Wool Industry

Papain is sometimes usedd to remove overlapping and emerging scales of wool (made of protein), thus, to give silky appearance and to avoid shrinkage of the wool. But this treatment is very costly.

6. Energy Field

Cellulase from the fungi Trichoderma viridi and Aspergillus niger is used to treat cellulosic raw plants materials for ethanol (used to blend petrol, called gasohol) production by the yeast.

Efforts are also being made by genetic engineering technology to obtain improved enzymes or to create new enzyme activities by making suitable changes in amino acid sequence of the enzymes.



  1. What are enzymes? Describe in brief the industrial applications of various enzymes.
  2. Discuss the various applications of immobilized enzymes giving suitable examples.
  3. Write short notes on:


(ii) Substrate saturation .

(iii) Enzymes in medicine

(iv) Advantages and disadvantages of enzyme immobilization

(v)Advantages and disadvantages of purified enzymes

(vi)Mode (mechanism) of action of enzymes

(vii)Abzymes and ribozymes

4. Describe the role of various enzymes in food industry.