June 12, 2021


5 min read





In this article, we are going to discuss enzyme definition.  Basically, enzymes are globular proteins that take part in the catalysis of chemical reactions. We will also learn their discovery, characteristics, and uses.


Enzymes are protein in nature. They speed up (catalyze) the chemical reactions and remain unchanged during chemical reactions. In living things they act as biocatalyst and maintain all metabolism (catabolism and anabolism) occurring in living cells. Every chemical reaction needs activation energy and acts as a barrier to start the reaction. By decreasing the need for activation energy, they break such barriers. The substances at which enzymes act are called substrates, and they convert substrates into different molecules called Products.


The term enzyme was first used By German physiologist Wilhelm Kuhne. Like other proteins, they are consist of a long chain of amino acids to form a three-dimensional molecule.

Components of enzyme;

  • Apo enzyme: This is the protein portion of an enzyme or an enzyme with its co-enzyme or prosthetic group removed is known as the Apo enzyme.
  • Cofactor: This is the non-protein portion of the enzyme, which plays its important role in the functioning of the enzyme. The cofactor generally acts as a bridge between an enzyme and its substrate, sometimes it takes part directly in a chemical reaction which speeds up the reaction (catalysis) or provides chemical energy, assisting to a chemical reaction that would be otherwise, very difficult or impossible. Some metal ions act as cofactors e.g. Zn2+, Cu2+, Fe2+ or Mg2+. There are two types of cofactors, (1) prosthetic group (2) co-enzyme. If the non-protein part is covalently bonded, this is the prosthetic group. On the other hand, if it is loosely attached to the protein part, it is called a co-enzyme. It is closely related to vitamins.
  • Holo-enzyme: An activated enzyme composed of a long chain of polypeptide and cofactor is called holo-enzyme.


Characteristics of the enzyme are briefly mentioned as under;

  1. They are highly specific in their substrates
  2. Speed up the chemical reaction.
  3. Some need co-enzyme
  4. Are affected by temperature
  5. Don’t consume in the chemical reactions
  6. They are affected by PH.
  7. They are needed in a small amount.
  8. Some of them catalyze reversible reactions
  9. They are inhibited by inhibitors.


  • All most enzymes consist of protein.
  • Most enzyme reaction rates are millions of times faster than those of comparable uncatalyzed reactions. Enzymes taking part in the chemical reactions do not consume by the reaction they catalyzed.
  • Enzymes are very specific for the nature of their substrates.
  • They are also very specific for the type of metabolism.
  • An only a small portion of enzyme molecules is directly involved in catalysis. This catalytic region is called the active site. It detects and combines with its substrate and starts catalysis.
  • Several pathways can work together in a particular order, creating metabolic pathways. In a metabolic pathway, one enzyme takes the product of another enzyme as a substrate. After the reaction, the substrates are transferred to the next enzyme.
  • Co-enzymes transport chemical substances from one enzyme to another. Some important vitamins (riboflavin, thiamin, and folic acid) act as co-enzymes.
  • Enzyme production can be increased or decreased by a cell according to the cell’s requirement. Their activity can also be controlled by inhibitors and activators.


On the basis of biochemical reactions taking place in living things, there are 6 categories of enzymes;

  • These enzymes are responsible for transferring the functional group from one molecule to another. e.g. alanine aminotransferase shuffles the alpha-amino group between alanine and aspartate. Some transferases also transfer phosphate between ATP and other compounds.
  • These enzymes take part in the process of hydrolysis, (Hydro=water and lysis=break down). Actually, they break the single bond with the addition of water. Some hydrolases function as digestive enzymes because they break peptide bonds in a protein.
  • Such types of enzymes catalyze reactions where functional groups are added to break double bonds in molecules where double bonds are formed by the removal of functional groups. For example, pyruvate decarboxylase removes CO2 from pyruvate.
  • These enzymes perform a function that is opposite to that of hydrolases. As we know that hydrolases break bonds by adding water, ligases form bonds by the removal of water components. There are different types of ligases involve in the synthesis of ATP.
  • These enzymes catalyze reactions where a functional group is removed to another position within the same molecule such that the resulting molecule is actually an isomer of the previous molecule. e.g. triosephosphate isomerase and phosphoglucose isomerase for converting 6-phosphate to fructose6-phosphate.
  • Oxidoreductases: These enzymes bring about oxidation and reduction reactions and hence called oxidoreductases.. When a substrate is being oxidized, these enzymes act as hydrogen donors. These enzymes are also called dehydrogenases or reductases. When the oxygen atom is the acceptor, these enzymes are termed oxidases.



We know that enzymes are biocatalysts and because of their significant properties, they are abundantly used in medical fields for diagnostic purposes. Researches,  in the last twenty years, have concentrated more on enzymes e.g. creatine kinase-MB, alanine transaminase, acid phosphatase, and alkaline phosphatase, etc.

Enzymatic diagnosis is a method to diagnose diseases by measuring the content and changes of certain substances in the body, or through the changes of the real activity of enzymes in the body. For example, glucose oxidase used to find out glucose concentration in diabetes diagnosis. Another example is the use of urease that detects urea in the diagnosis of liver and kidney lesions. Similarly, cholesterol oxidase can be used to measure the content of cholesterol in the blood to diagnose hyperlipidemia.


Enzymes are used in the food, agriculture, and pharmaceutical industries to

speed up and control the reactions in order to quickly and more accurately valuable final products. For example, cheese making is an old tradition that needs a few ingredients such as milk, bacteria, and rennet. Rennet is an enzyme that breaks down the milk protein casein to form the cheese curd.


                              The uses of enzymes in detergents are the same as their uses in the body. For example lipases and proteases process any remnants of protein, starches, and fats in the clothing.

Once the enzymes have done their job, the broken down particles can easily be removed away with the warm water in the washing machine, hence with a biological detergent like Persil power gems you can be sure you are tackling stains head-on.


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