There are many chemical reactions in every living cell. Enzymes (enzymes) are proteins with special and extremely important functions. They are called biocatalysts. The main function of protein enzymes in the body is to accelerate biochemical reactions. The initial reagents, the interaction of which is catalyzed by these molecules, are called substrates, and the final compounds are called products.
In nature, enzyme proteins work only in living systems. But in modern biotechnology, clinical diagnostics, pharmaceuticals and medicine, purified enzymes or their complexes are used, as well as additional components necessary for the operation of the system and visualization of data for the researcher.
Biological significance and properties of enzymes
Without these molecules, a living organism would not be able to function. All life processes work harmoniously thanks to enzymes. The main function of enzyme proteins in the body is to regulate metabolism. Without them, normal metabolism is impossible. Molecular activity is regulated byactivators (inductors) or inhibitors. The control acts at different levels of protein synthesis. It also "works" in relation to the finished molecule.
The main property of protein-enzymes is specificity to a certain substrate. And, accordingly, the ability to catalyze only one or less often a number of reactions. Usually such processes are reversible. One enzyme is responsible for both functions. But that's not all.
The role of enzyme proteins is essential. Without them, biochemical reactions do not proceed. Due to the action of enzymes, it becomes possible for the reagents to overcome the activation barrier without significant expenditure of energy. In the body there is no way to heat the temperature above 100 ° C or use aggressive components like a chemical laboratory. The enzyme protein binds to the substrate. In the bound state, modification occurs with the subsequent release of the latter. This is how all catalysts used in chemical synthesis work.
What are the levels of organization of an enzyme protein molecule?
Usually these molecules have a tertiary (globule) or quaternary (several connected globules) protein structure. First, they are synthesized in a linear form. And then they are folded into the required structure. To ensure activity, the biocatalyst needs a certain structure.
Enzymes, like other proteins, are destroyed by heat, extreme pH values, aggressive chemical compounds.
Additional propertiesenzymes
Among them, the following features of the components are distinguished:
- Stereospecific - the formation of only one product.
- Regioselectivity - breaking a chemical bond or modifying a group in only one position.
- Chemoselectivity - catalysis of only one reaction.
Features of work
Enzyme specificity varies. But any enzyme is always active in relation to a specific substrate or group of compounds similar in structure. Non-protein catalysts do not have this property. Specificity is measured by the binding constant (mol/l), which can be as high as 10−10 mol/l. The work of the active enzyme is rapid. One molecule catalyses thousands to millions of operations per second. The degree of acceleration of biochemical reactions is significantly (1000-100000 times) higher than that of conventional catalysts.
The action of enzymes is based on several mechanisms. The simplest interaction occurs with one substrate molecule, followed by the formation of a product. Most enzymes are able to bind 2-3 different molecules that react. For example, the transfer of a group or atom from one compound to another, or double substitution according to the "ping-pong" principle. In these reactions, one substrate is usually connected, and the second is associated through a functional group with the enzyme.
The study of the mechanism of enzyme action occurs using methods:
- Definitions of intermediate and final products.
- Studies of the geometry of the structure and functional groups associated withsubstrate and provide a high reaction rate.
- Mutation of enzyme genes and determination of changes in its synthesis and activity.
Active and connecting center
A substrate molecule is much smaller than an enzyme protein. Therefore, binding occurs due to a small number of functional groups of the biocatalyst. They form an active center, consisting of a specific set of amino acids. In complex proteins, a prosthetic group of a non-protein nature is present in the structure, which can also be part of the active center.
It is necessary to single out a separate group of enzymes. Their molecule contains a coenzyme that constantly binds to the molecule and is released from it. A fully formed enzyme protein is called a holoenzyme, and when the cofactor is removed, it is called an apoenzyme. Vitamins, metals, derivatives of nitrogenous bases often act as coenzymes (NAD - nicotinamide adenine dinucleotide, FAD - flavin adenine dinucleotide, FMN - flavin mononucleotide).
The binding site provides substrate specificity. Due to it, a stable substrate-enzyme complex is formed. The structure of the globule is constructed in such a way as to have a niche (slit or depression) of a certain size on the surface, which ensures the binding of the substrate. This zone is usually located not far from the active center. Some enzymes have sites for binding to cofactors or metal ions.
Conclusion
Protein-The enzyme plays an important role in the body. Such substances catalyze chemical reactions, are responsible for the process of metabolism - metabolism. In any living cell, hundreds of biochemical processes are constantly taking place, including reduction reactions, splitting and synthesis of compounds. Oxidation of substances constantly occurs with a large release of energy. It, in turn, is spent on the formation of carbohydrates, proteins, fats and their complexes. Cleavage products are the building blocks for the synthesis of the necessary organic compounds.
