Protein-enzyme: the role, properties, function of protein-enzymes in the body

In every living cell, many chemical reactions occur. 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 whose interaction is catalyzed by these molecules are called substrates, and the final compounds are 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 system operation and data visualization for the researcher.

Biological significance and properties of enzymes

Without these molecules, a living organism could not function. All processes of vital activity work together thanks to enzymes. The main function of protein-enzymes in the body is the regulation of the metabolism. Without them, normal metabolism is impossible. The regulation of the activity of molecules occurs under the action of activators (inducers) or inhibitors. Control acts at different levels of protein synthesis. He also "works" for an already ready molecule.

The main properties of protein-enzymes are specificity to a certain substrate. And, accordingly, the ability to catalyze only one or, rarely, a series of reactions. Usually, such processes are reversible. Both enzymes are responsible for both functions. But that is not all.

The role of protein-enzymes 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 expenditure. In the body, it is not possible to heat the temperature more than 100 ° C or use aggressive components like a chemical laboratory. The protein-enzyme combines with the substrate. In the bound state, a modification occurs, followed by the release of the latter. This is how all catalysts used in chemical synthesis work.

What are the levels of organization of the protein-enzyme 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 fold into the required structure. To ensure activity, the biocatalyst needs a certain structure.

Enzymes, like other proteins, are destroyed by heating, extreme pH, aggressive chemical compounds.

Additional properties of enzymes

Among them, the following features of the components are distinguished:

1. Stereospecificity - the formation of only one product.
2. Regioselectivity is the breaking of a chemical bond or the modification of a group in only one position.
3. Chemoselectivity is the catalysis of only one reaction.

Features of work

The level of specificity of enzymes varies. But any enzyme is always active with respect to a particular substrate or group of compounds, similar in structure. Non-protein catalysts do not have this property. The specificity is measured by the binding constant (mol / l), which can reach 10 ^-10 mol / l. The work of the active enzyme is rapid. One molecule catalyzes thousands of 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 a product. Most enzymes are able to bind 2-3 different molecules that enter into the reaction. For example, the transfer of a group or atom from one connection to another or a double substitution on the principle of "ping-pong." In these reactions, one substrate is usually connected, and the second is bound via a functional group to the enzyme.

The mechanism of action of the enzyme is studied using the following methods:

1. Definitions of intermediate and final products.
2. Studies of the geometry of structure and functional groups associated with the substrate and providing a high reaction rate.
3. Mutations of the enzyme genes and determining changes in its synthesis and activity.

Active and binding center

The molecule of the substrate is much smaller in size than the protein-enzyme. 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 in the structure there is a prosthetic group of non-protein nature, which can also be part of the active center.

It is necessary to single out a separate group of enzymes. They have a coenzyme in the molecule that constantly binds to the molecule and is released from it. A fully formed protein-enzyme is called a holoenzyme, and when the cofactor is removed, it is called an apoenzyme. Vitamins, metals, derivatives of nitrogenous bases (NAD - nicotinamide adenine dinucleotide, FAD - flavinadenine dinucleotide, FMN - flavinmonucleotide) are often used as coenzymes.

The binding center provides specificity of affinity to 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 on the surface a niche (gap or cavity) of a certain size, which ensures the binding of the substrate. This zone is usually located not far from the active center. Individual enzymes have sites for coupling with cofactors or metal ions.

Conclusion

The protein-enzyme plays an important role in the body. Such substances catalyze chemical reactions, are responsible for the metabolic process - metabolism. In any living cell, hundreds of biochemical processes constantly occur, including the reductive reactions, the cleavage and synthesis of compounds. Oxidation of substances with a large release of energy is constantly occurring. It, in turn, is spent on the formation of carbohydrates, proteins, fats and their complexes. The cleavage products are the structural elements for the synthesis of the necessary organic compounds.