Induced fit Hypothesis

The substrate gets attached to the enzyme which has a specific structure that can only be fitted in a particular enzyme. In Induced fit, the active site is not exactly complementary to the substrate but changes shape in the presence of a specific substrate to become complementary and initiate the reaction. When a substrate molecule interacts with an enzyme, if its composition is specifically correct, the shape of the enzyme’s Active site will change so that the substrate fits into it and an Enzyme – Substrate complex can be formed. After the reaction, an Enzyme-Product Complex is formed. The enzyme slows down the activation energy of the reaction by providing a surface to the substrate. The intermediate state where the substrate binds with the enzyme is called the transition state. The enzyme and substrate form bonds and then breaks them, which results in a product and later they split into product and enzyme. The enzymes then bind to other substrates the cycle continues till the reaction is completed. When the substrate (S) binds to its active site with the enzyme (E), a complex (intermediate ES) is developed which produces the product (P) and the enzyme. 

The steps included in enzyme actions are:

• Step 1: The enzyme and substrate combine and result in an intermediate substrate.
• Step 2: The detachment of complex molecules gives the product and enzyme. 

The entire catalyst reaction of enzymes can be expressed as:

E  +  S  —>  (ES)  —>   E  +  P

Different types of cells, tissue, and other complex organs together form the human body. Our body releases some chemicals for the effective functioning of the body and to improve biological processes such as respiration, digestion, excretion, and a few other metabolic activities to maintain a healthy life. Hence, enzymes are essential for biological processes in all living organisms. 

Enzymes can be defined as biological polymers produced by living organism that catalyze the biochemical reactions. 

They are basically proteins that are produced by living organisms inside the body that help in facilitating certain metabolic and biochemical reactions. These are the biological catalysts that speed up the metabolic reaction inside the body. Enzymes are crucial for metabolic processes and other chemical reactions in the cell. They are necessary for sustaining the life of organisms. Enzymes are catalysts, so they do not involve directly in biological reactions but they help with their efficient occurrence. The metabolic processes depend on the enzymes which react with the molecule and are called the substrate. Enzymes convert the substrates into other distinct molecules known as products. Mostly they are found in all tissues and fluids of the body. The essential and critical life processes are exhibited based on the function of enzymes. The enzymes in the plasma membrane control the catalysis in the cells due to the response of cellular signals and enzymes in circulatory systems regulate the clotting of blood. 

Structure of Enzymes

Enzymes are mostly proteins. They have a primary structure i.e. linear chain of amino acids, which eventually form a three-dimensional shape. An enzyme like any protein has secondary and tertiary structures. In tertiary structure, the protein chains fold upon themselves, and the chain crisscrosses upon itself which creates many pockets or crevices. One such pocket is known as the ‘active site’ or the substrate-binding site. The substrate fits into a pocket or crevice which is the active site of an enzyme. Thus, the active site of an enzyme catalyzes the biochemical reactions at a high rate. The enzymes are able to break the bigger molecule into simpler molecules or vice versa. Enzymes get damaged at high temperatures (above 40^oc) and high pressure, resulting in loss of enzyme activity. Thermal stability is thus an important factor of such enzymes. 

Enzymes are eventually larger with varying sizes, as compared to their substrate, ranging from 62 amino acid residues to 2500 residues found in fatty acid synthase. These amino acids are liked in a specific way to form different types of enzymes. Only a small part of the entire enzyme structure is used for catalysis and is situated next to binding sites. The enzyme’s active site consists of both the catalytic site and binding site together. The enzymes also have a site called the inhibitor site. This site is functional when the enzyme is in the inactivated state. The enzymes also have a model of lock and key structure. The active site of an enzyme is flexible and can be modified, and thus can be reshaped based on the interactions with corresponding substrates. 

What do enzymes do?

Enzymes are not living organisms and are a particular type of protein that helps in speeding up the biochemical reaction in our body. Each cell in the human body contains thousands of enzymes. Enzymes provide help with facilitating chemical reactions within each cell. As they are not destroyed during the process, a cell can reuse each enzyme repeatedly. The presence of these enzymes helps in many reactions inside the body that keep a person alive and well. They are important for digestion, oxidation, hydrolysis, respiration, muscle and nerve function, liver function, and much more. Enzymes in our blood assist with healthcare and check for injuries and diseases. Enzymes in our body catalyze all kinds of chemical reactions that include growth, blood clotting, diseases, breathing, etc.