Mechanism of Enzyme Action

Introduction

An enzyme is a material that functions as a catalyst in living organisms, controlling the pace at which chemical reactions occur while avoiding being altered in the process. It is a protein.

In all living creatures, biological processes are chemical reactions, and enzymes are responsible for the majority of these chemical reactions. Many of these reactions would not occur at all if enzymes were not there to speed up the process.

 Enzymes are responsible for the catalysis of all elements of cell metabolism. In this process, big nutrition molecules (such as proteins, carbohydrates, and lipids) are broken down into smaller molecules, and chemical energy is conserved and transformed. In addition, cellular macromolecules are constructed from smaller precursors, which is known as a cellular assembly. In many inherited human disorders, such as albinism and phenylketonuria, a shortage of a specific enzyme is the underlying cause of the condition.

Enzymes offer a variety of useful industrial and medical applications as well. Although the fermentation of wine, leavening of bread, curdling of cheese, and brewing of beer have all been conducted since the beginning of time, it was not until the nineteenth century that it was realized that these events were the result of the catalytic activity of enzymes. 

The use of enzymes has increased steadily throughout the years, particularly in industrial operations that include organic chemical reactions. Enzymes are used in medicine for a variety of purposes, including destroying disease-causing microbes, improving wound healing, and identifying certain disorders.

Chemical Nature

It was formerly believed that all enzymes were proteins, however, research has shown that some nucleic acids, known as ribozymes (or catalytic RNAs), can catalyse enzyme activity, thereby disproving this premise. This discussion will be mostly focused on protein enzymes due to the fact that so little is known about the enzymatic functioning of RNA at this time.

A big protein enzyme molecule is made up of one or more amino acid chains known as polypeptide chains, which are linked together. A protein’s structure is determined by its amino acid sequence, which is critical for enzyme specificity since it dictates the protein’s folding patterns. If the enzyme is subjected to changes, such as temperature or pH fluctuations, the protein structure may become denatured, and the enzyme’s enzymatic capacity may be impaired. Denaturation can be reversed in some cases, but not all of them.

Some enzymes are associated with an extra chemical component known as a cofactor, which is a direct participant in the catalytic action and, as a result, is required for the enzyme to function. When it comes to cofactors, they can take the form of either an organic molecule (such as a vitamin) or an inorganic metal ion; however, certain enzymes require both. A cofactor can be either securely or loosely linked to an enzyme, depending on its function. The cofactor is referred to as a prosthetic group if it is strongly coupled to the other cofactors.

Mechanism of Enzyme Action

In the majority of chemical reactions, there is an energy barrier that must be overcome in order for the reaction to take place. Complex molecules such as proteins and nucleic acids are protected from degradation by this barrier, which is essential for the survival of all living organisms, including bacteria. 

Certain of these complex molecules, however, must be broken down in order for metabolic changes to occur in a cell, and this energy barrier must be overcome. Heat may be able to give the additional energy required (known as activation energy), but the increase in temperature would cause the cell to die. The use of a catalyst can lower the activation energy level, which is an alternative to using a catalyst. 

This is the function that enzymes do. Because of their reactivity with the substrate, they produce an intermediate complex (also known as a “transition state”) that takes less energy for the reaction to occur. The unstable intermediate complex decomposes rapidly to create reaction products, leaving the enzyme unaffected and free to react with other substrate molecules in the presence of the enzyme.

Only a specific area of the enzyme, referred to as the active site, is capable of binding to the substrate. The active site is a groove or pocket generated by the protein’s folding arrangement, and it is where the enzyme functions.

As a result of this three-dimensional structure, together with the chemical and electrical properties of the amino acids and cofactors within the active site, the enzyme can only bind to a certain substrate, hence determining its specificity.

The genetic control and distribution of enzymes within a cell have an impact on the synthesis and activity of enzymes. A number of enzymes are not created by some cells, while others are only produced when they are required. Unlike proteins, enzymes are not typically distributed in the same locations throughout a cell; they are frequently compartmentalised in the nucleus, on the cell membrane, or in subcellular structures. Hormones, neurosecretions, and other substances that modify the cell’s internal environment have an additional impact on the rates of enzyme synthesis and activity.

Factors Affecting Enzyme Activity

The fact that enzymes are not consumed during the reactions that they catalyse and can be reused multiple times means that only a very minimal quantity of an enzyme is required to catalyse a given reaction. Each second, an enzyme molecule can transform 1,000 substrate molecules into active enzyme molecules. 

The rate of an enzymatic reaction increases as the concentration of the substrate increases, reaching its maximum velocity when all of the enzyme molecules’ active sites are occupied by the substrate. As a result, the enzyme has reached saturation, and the rate of the reaction is determined by the rate at which the active sites can convert substrate into the desired product. Inhibiting enzyme activity can be accomplished in a variety of ways. 

It is possible to experience competitive inhibition when molecules that are highly similar to the substrate molecules attach to the active site and prevent the actual substrate from binding. A competitive inhibitor such as penicillin, for example, prevents bacteria from constructing their cell walls by binding to the active site of an enzyme that many bacteria employ.

Allosteric control of enzyme activity can involve both stimulation and inhibition of enzyme activity. In some cases, an activator molecule can be coupled to an allosteric site and initiate a reaction at the active site by changing its shape to fit a substrate that would not otherwise be able to induce the change. 

Hormones and the results of previous enzymatic reactions are examples of activators that are commonly encountered. Allosteric stimulation and inhibition allow the cell to produce energy and materials when they are required while inhibiting production when the supply is sufficient.

Conclusion

Enzymes are biological catalysts that speed up the rate at which cellular reactions take place. The following is the mechanism of enzyme catalysis: A huge molecular mass ranging from 12000 to 40,000 is characteristic of enzymes, which are proteins (globular proteins). As a result, they are far larger than the molecules that they catalyse. Enzymes are necessary for life and are one of the most significant forms of protein found in the human body, accounting for around a third of total protein. The study of enzyme kinetics gives information about the wide spectrum of reactions that take place in the human body, which we may utilise to better understand and anticipate the metabolism of all living creatures on the planet.