Enzymes
In living organisms, a biomolecule is a chemical substance. Chemicals mostly made up of carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus fall within this category. Biomolecules are the fundamental building elements of life and play critical roles in living creatures. Amino acids, lipids, carbohydrates, proteins, polysaccharides, and nucleic acids are examples of biomolecules.
Enzymes are nitrogenous organic molecules produced by living organisms such as plants and animals. A long chain of one or more amino acids is connected together using amide or peptide bonds to make them.
They are high-molecular-mass proteins that catalyse natural processes in the bodies of animals and plants. They are also known as polypeptides. Enzymes are categorised into distinct categories based on their structure and properties. Enzymes have a specific method of action (Lock-and-Key mechanism and Enzyme Fit Hypothesis).
Structure of Enzyme
Enzymes are proteins that are made up of several polypeptide chains, also known as amino acids, that have been folded and coiled numerous times.
They have linear chains of amino acids in three-dimensional structures.
The enzyme’s catalytic activity is determined by the amino acid sequence. Only a small portion of an enzyme’s structure participates in catalysis and is located around the binding sites.
They have separate sites; the active site of an enzyme is made up of the catalytic and binding sites.
Classification of Enzymes
The International Union of Biochemists divides enzymes into six types based on the sort of reaction they catalyse (I U B). Oxidoreductases, transferases, hydrolases, lyases, ligases, and isomerases are the six types of enzymes. The following are their functions:
Oxidoreductases: Oxidoreductase is an enzyme that catalyses the oxidation and reduction reactions in which electrons are transferred from one form of a molecule (electron donor) to the other (electron acceptor). Consider the enzyme pyruvate dehydrogenase. Cofactors for oxidoreductase enzymes are commonly NADP+ or NAD+.
Transferases: These catalyse the transfer of a chemical group (functional group) from one compound (referred to as the donor) to another compound (referred to as the recipient) (called the acceptor). A transaminase, for example, is an enzyme that transfers an amino group from one molecule to another.
Hydrolases: They are hydrolytic enzymes that catalyse the hydrolysis reaction by cleaving the bond and hydrolyzing it with water molecules, i.e. they catalyse the hydrolysis of a bond. Pepsin, for example, breaks down peptide connections in proteins.
Lyases: They are enzymes that catalyse bodywork by creating a double bond or adding a group to a double bond without involving hydrolysis or oxidation. Aldolase (a glycolysis enzyme) catalyses the conversion of fructose-1, 6-bisphosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, for example.
Isomerases: They’re an enzyme family that converts a chemical from one isomer to another. Isomerases aid intramolecular rearrangements by breaking as well as forming bonds. In glycogenolysis, for example, phosphoglucomutase catalyses the conversion of glucose-1-phosphate to glucose-6-phosphate (the phosphate group is moved from one position to another in the same substance). For energy to be released fast, glycogen is converted to glucose.
Ligases: Ligase is a catalytic enzyme that catalyses the ligation or connecting of two big molecules by establishing a new chemical link between them. DNA ligase, for example, catalyses the formation of a phosphodiester bond between two DNA fragments.
Enzyme Cofactor
Cofactors are chemical substances that are not proteins and are found in enzymes. A cofactor affects the action of an enzyme by acting as a catalyst. Apoenzymes are enzymes that do not require a cofactor. The holoenzyme is made up of an enzyme and its cofactor.
Three Kinds of Cofactors Present in Enzymes:
Prosthetic groups: These are cofactors that are always covalently or permanently linked to an enzyme. Many enzymes have a FAD (Flavin Adenine Dinucleotide) prosthetic group.
Coenzyme: A coenzyme is a non-protein organic molecule that only interacts to an enzyme during catalysis. It is separated from the enzyme at all other times. NAD+ is a widely used coenzyme.
Metal ions: Certain enzymes require a metal ion in the active site to establish coordinate bonds during catalysis. A number of enzymes use the metal ion cofactor Zn2+.
Mechanism of Enzyme Action
The active site of an enzyme draws substrates and catalyses the chemical process that produces products. Allows the products to disassociate or detach from the enzyme’s surface after product production. The enzyme-substrate complex is the combination of an enzyme and its substrates.
The reaction requires the collision of any two molecules, as well as the correct orientation and a sufficient quantity of energy.
This energy must be transferred between these molecules in order to overcome the reaction’s Activation Energy barrier. Without any catalysts, the substrate and enzyme produce an intermediate reaction with low activation energy.
Two of the most well-known mechanisms of enzyme function are the Induced Fit Hypothesis and the Lock and Key Mechanism.
Induced Fit Hypothesis: In 1958, Daniel Koshland proposed the induced fit model. One of the most common models for characterising the enzyme-substrate interaction is this one. The active site of the enzyme, according to the idea, does not have a firm shape. As a result, the substrate does not completely fit into the enzyme’s active site. As a result, when the enzyme binds to the substrate, the active site changes form, becoming complementary to the substrate’s shape. Because of the flexibility of the protein, this conformational shift is possible.
Lock and Key Mechanism: Emil Fischer proposed the lock and key concept in 1894, and it is now known as Fisher’s theory, which describes the enzyme-substrate interaction. Emil Fischer proposed the lock and key model in 1894. As a result, it’s sometimes referred to as Fisher’s theory. The enzyme-substrate interaction is described by the second model.
The enzyme’s active site functions as the ‘lock,’ while its substrate serves as the ‘key,’ according to the lock and key concept. As a result, the form of the enzyme’s active site complements the shape of the substrate. By generating an useless intermediate product, the enzyme-substrate complex, the active site of the enzyme can hold the substrate closer to the enzyme.