In every living cell, many chemical reactions take place. 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 starting reagents, the interaction of which is catalyzed by these molecules, are called substrates, and the final compounds are called products.
In nature, protein enzymes 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 system to work and visualize data for the researcher.
Biological significance and properties of enzymes
Without these molecules, a living organism could not function. All life processes work harmoniously thanks to enzymes. The main function of protein enzymes in the body is the regulation of metabolism. Without them, normal metabolism is impossible. Regulation of the activity of molecules occurs under the influence of activators (inducers) or inhibitors. Control acts at different levels of protein synthesis. He also โworksโ with respect to the finished molecule.
The main properties of protein enzymes are specificity for a particular substrate. And, accordingly, the ability to catalyze only one or less often a series of reactions. Typically, these processes are reversible. For the performance of both functions, one enzyme is responsible. But that is not all.
The role of enzyme proteins is essential. Without them, biochemical reactions do not occur. Due to the action of enzymes, it becomes possible for reagents to overcome the activation barrier without significant energy expenditures. In the body there is no way to heat the temperature above 100 ยฐ C or use aggressive components like a chemical laboratory. The protein enzyme binds to the substrate. In a bound state, a modification occurs with the subsequent release of the latter. This is how all the catalysts used in chemical synthesis work.
What are the levels of organization of a protein-enzyme molecule?
Typically, 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 collapsed into the required structure. To ensure activity, the biocatalyst needs a certain structure.
Enzymes, like other proteins, are destroyed by heating, extreme pH, and aggressive chemical compounds.
Additional properties of enzymes
Among them, the following features of the components are distinguished:
- Stereospecificity - the formation of only one product.
- Regioselectivity - breaking a chemical bond or modifying a group in only one position.
- Chemoselectivity is the catalysis of only one reaction.
Features of work
The level of specificity of enzymes varies. But any enzyme is always active against a specific substrate or group of compounds that are similar in structure. Non-protein catalysts do not have this property. Specificity is measured by the binding constant (mol / L), which can reach 10 โ10 mol / L. The work of the active enzyme is fast. One molecule catalyzes thousands and 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 built on several mechanisms. The simplest interaction occurs with one molecule of the substrate, followed by the formation of the product. Most enzymes are able to bind 2-3 different molecules that enter into a reaction. 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 combined, and the second binds via an functional group to the enzyme.
The study of the mechanism of action of the enzyme occurs using methods:
- Definitions of intermediates and end products.
- Studying the geometry of the structure and functional groups associated with the substrate and providing a high reaction rate.
- Mutations of enzyme genes and determination of changes in its synthesis and activity.
Active and binding center
The substrate molecule is much smaller than the protein enzyme. Therefore, binding occurs due to the 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.
A separate group of enzymes should be distinguished. They have a coenzyme in the molecule, which is constantly bound to the molecule and freed from it. A fully formed protein enzyme is called holoenzyme, and when the cofactor is removed, it is called an enzyme. Coenzymes are often vitamins, metals, derivatives of nitrogen bases (NAD - nicotinamide adenine dinucleotide, FAD - flavin adenine dinucleotide, FMN - flavin mononucleotide).
The binding center ensures the specificity of the affinity for the substrate. 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 (gap or cavity) on the surface of a certain size, which provides binding of the substrate. This zone is usually located near the active center. Individual enzymes have sites for bonding with cofactors or metal ions.
Conclusion
Protein-enzyme plays an important role in the body. Such substances catalyze chemical reactions, are responsible for the metabolism - metabolism. In any living cell, hundreds of biochemical processes constantly occur, including reducing reactions, splitting and synthesis of compounds. Constantly oxidation of substances with a large release of energy. It, in turn, is spent on the formation of carbohydrates, proteins, fats and their complexes. Cleavage products are structural elements for the synthesis of the necessary organic compounds.