Squirrels- natural polypeptides with a huge molecular weight. They are part of all living organisms and perform various biological functions.
Protein structure.
Proteins have 4 levels of structure:
- protein primary structure- linear sequence of amino acids in a polypeptide chain, folded in space:
- protein secondary structure- conformation of the polypeptide chain, because twisting in space due to hydrogen bonds between N.H. And CO in groups. There are 2 installation methods: α -spiral and β - structure.
- protein tertiary structure is a three-dimensional representation of a swirling α -spiral or β -structures in space:
This structure is formed by -S-S- disulfide bridges between cysteine residues. Oppositely charged ions participate in the formation of such a structure.
- protein quaternary structure is formed due to the interaction between different polypeptide chains:
Protein synthesis.
The synthesis is based on a solid-phase method, in which the first amino acid is fixed on a polymer carrier, and new amino acids are sequentially added to it. The polymer is then separated from the polypeptide chain.
Physical properties of protein.
The physical properties of a protein are determined by its structure, so proteins are divided into globular(soluble in water) and fibrillar(insoluble in water).
Chemical properties of proteins.
1. Protein denaturation(destruction of the secondary and tertiary structure while maintaining the primary). An example of denaturation is the coagulation of egg whites when eggs are boiled.
2. Protein hydrolysis- irreversible destruction of the primary structure in an acidic or alkaline solution with the formation of amino acids. This way you can establish the quantitative composition of proteins.
3. Qualitative reactions:
Biuret reaction- interaction of the peptide bond and copper (II) salts in an alkaline solution. At the end of the reaction, the solution turns purple.
Xanthoprotein reaction- when reacting with nitric acid, a yellow color is observed.
Biological significance of protein.
1. Proteins are a building material; muscles, bones, and tissues are built from it.
2. Proteins - receptors. They transmit and perceive signals coming from neighboring cells from the environment.
3. Squirrels play important role V immune system body.
4. Proteins perform transport functions and transport molecules or ions to the site of synthesis or accumulation. (Hemoglobin carries oxygen to tissues.)
5. Proteins - catalysts - enzymes. These are very powerful selective catalysts that speed up reactions millions of times.
There are a number of amino acids that cannot be synthesized in the body - irreplaceable, they are obtained only from food: tisine, phenylalanine, methinine, valine, leucine, tryptophan, isoleucine, threonine.
Enzymatic hydrolysis of proteins occurs under the action of proteolytic enzymes (proteases). They are classified into endo- and exopeptidases. Enzymes do not have strict substrate specificity and act on all denatured and many native proteins, cleaving peptide bonds -CO-NH- in them.
Endopeptidases (proteinases) - hydrolyze proteins directly through internal peptide bonds. As a result, a large number of polypeptides and few free amino acids are formed.
Optimal conditions for the action of acid proteinases: pH 4.5-5.0, temperature 45-50 °C.
Exopeptidases (peptidases) act primarily on polypeptides and peptides by breaking the peptide bond at the end. The main products of hydrolysis are amino acids. This group enzymes are divided into amino-, carboxy-, and dipeptidases.
Aminopeptidases catalyze the hydrolysis of the peptide bond adjacent to the free amino group.
H2N - CH - C - - NH - CH - C....
Carboxypeptidases hydrolyze the peptide bond adjacent to the free carboxyl group.
CO -NH- C - H
Dipeptidades catalyze the hydrolytic cleavage of dipeptides into free amino acids. Dipeptidases cleave only those peptide bonds adjacent to which there are simultaneously free carboxyl and amine groups.
dipeptidase
NH2CH2CONHCH2COOH + H2O 2CH2NH2COOH
Glycine-Glycine Glycocol
Optimal operating conditions: pH 7-8, temperature 40-50 oC. The exception is carboxypeptidase, which exhibits maximum activity at a temperature of 50 °C and pH 5.2.
Hydrolysis of protein substances in the canning industry is necessary in the production of clarified juices.
Advantages of the enzymatic method for producing protein hydrolysates
When produced biologically active substances Of protein-containing raw materials, the most important is its deep processing, which involves the breakdown of protein molecules into constituent monomers. Promising in this regard is the hydrolysis of protein raw materials for the purpose of producing protein hydrolysates - products containing valuable biologically active compounds: polypeptides and free amino acids. Any natural proteins with complete amino acid composition, the sources of which are blood and its constituent components, can be used as raw materials for the production of protein hydrolysates; tissues and organs of animals and plants; dairy and food industry waste; veterinary confiscations; food and food products of low nutritional value obtained through processing various types animals, birds, fish; production waste from meat processing plants and glue factories, etc. When obtaining protein hydrolysates for medical and veterinary purposes, mainly proteins of animal origin are used: blood, muscle tissue And internal organs, protein shells, as well as whey proteins.
The problem of protein hydrolysis and its practical implementation have attracted the attention of researchers for a long time. Based on the hydrolysis of proteins, it is obtained various drugs, widely used in practice: as blood substitutes and for parenteral nutrition in medicine; to compensate for protein deficiency, increase resistance and improve the development of young animals in veterinary medicine; as a source of amino acids and peptides for bacterial and culture media in biotechnology; in the food industry, perfumery. Quality and properties of protein hydrolysates intended for various applications, are determined by the feedstock, the method of hydrolysis and subsequent processing of the resulting product.
Varying the methods for obtaining protein hydrolysates makes it possible to obtain products with desired properties. Depending on the amino acid content and the presence of polypeptides in the range of the corresponding molecular weight, the region of most effective use hydrolysates. Protein hydrolysates obtained for various purposes are subject to different requirements, depending primarily on the composition of the hydrolyzate. Thus, in medicine it is desirable to use hydrolysates containing 15...20% free amino acids; in veterinary practice, to increase the natural resistance of young animals, the content of peptides in hydrolysates is predominant (70...80%); For food purposes, the organoleptic properties of the resulting products are important. But the main requirement when using protein hydrolysates in various fields is a balanced amino acid composition.
Protein hydrolysis can be accomplished in three ways: by the action of alkalis, acids and proteolytic enzymes. Alkaline hydrolysis of proteins produces lanthionine and lysinoalanine residues, which are toxic to humans and animals. This hydrolysis destroys arginine, lysine and cystine, so it is practically not used to obtain hydrolysates. Acid hydrolysis of protein is a widely used method. Most often, protein is hydrolyzed with sulfur or hydrochloric acid. Depending on the concentration of the acid used and the hydrolysis temperature, the process time can vary from 3 to 24 hours. Hydrolysis with sulfuric acid is carried out for 3...5 hours at a temperature of 100...130 °C and a pressure of 2...3 atmospheres; hydrochloric - for 5...24 hours at the boiling point of the solution under low pressure.
With acid hydrolysis, a greater depth of protein breakdown is achieved and the possibility of bacterial contamination of the hydrolyzate is eliminated. This is especially important in medicine, where hydrolysates are used mainly parenterally and it is necessary to exclude anaphylactogenicity, pyrogenicity and others. undesirable consequences. IN medical practice Acid hydrolysates are widely used: aminokrovin, hydrolysin L-103, TsOLIPK, infusamine, gemmos and others.
The disadvantage of acid hydrolysis is the complete destruction of tryptophan, partial destruction of hydroxyamino acids (serine and threonine), deamination of the amide bonds of asparagine and glutamine with the formation of ammonia nitrogen, destruction of vitamins, as well as the formation of humic substances, the separation of which is difficult. In addition, when neutralizing acid hydrolysates, a large amount of salts is formed: chlorides or sulfates. The latter are especially toxic to the body. Therefore, acid hydrolysates require subsequent purification, for which ion exchange chromatography is usually used in production.
To avoid the destruction of labile amino acids in the process of obtaining acid hydrolysates, some researchers used mild hydrolysis regimes in an inert gas atmosphere and also added antioxidants, thioalcohols or indole derivatives to the reaction mixture. Acid and alkaline hydrolysis, in addition to those indicated, also have significant limitations associated with the reactivity of the environment, which leads to rapid corrosion of equipment and necessitates compliance with strict safety requirements for operators. Thus, the technology of acid hydrolysis is quite labor-intensive and requires the use of complex equipment (ion exchange columns, ultramembranes, etc.) and additional stages of purification of the resulting drugs.
Research has been carried out on the development of electrochemical enzymatic technology for the production of hydrolysates. The use of this technology makes it possible to eliminate the use of acids and alkalis from the process, since the pH of the medium is ensured as a result of electrolysis of the processed medium containing a small amount of salt. This, in turn, allows you to automate the process and provide more precise and operational control of process parameters.
As is known, in the body protein is under the influence of digestive enzymes breaks down into peptides and amino acids. Similar cleavage can be carried out outside the body. To do this, pancreatic tissue, the mucous membrane of the stomach or intestines, pure enzymes (pepsin, trypsin, chymotrypsin) or enzyme preparations microbial synthesis. This method of protein breakdown is called enzymatic, and the resulting hydrolyzate is called enzymatic hydrolyzate. The enzymatic method of hydrolysis is more preferable compared to chemical methods, since it is carried out in “mild” conditions (at a temperature of 35...50°C and atmospheric pressure). The advantage of enzymatic hydrolysis is the fact that during its implementation, amino acids are practically not destroyed and do not enter into additional reactions (racemization and others). In this case, a complex mixture of protein breakdown products with different molecular weights is formed, the ratio of which depends on the properties of the enzyme used, the raw materials used and the process conditions. The resulting hydrolysates contain 10...15% total nitrogen and 3.0...6.0% amine nitrogen. The technology for carrying it out is relatively simple.
Thus, compared to chemical technologies, the enzymatic method for producing hydrolysates has significant advantages, the main ones being: accessibility and ease of implementation, low energy consumption and environmental safety.
Hydrolysis (hydrolysis) of proteins- This is the process of breaking up chains of protein molecules into parts.
The resulting fragments are called and have a number of useful properties. The main one is much faster absorption compared to the original molecule. Ideal protein hydrolysis is the breakdown of the protein molecule into its constituent amino acids. They form the basis of amino acid complexes - the most effective drugs from a supply point of view muscle cells building material. However, it does not always make sense to carry out a full hydrolysis cycle. To improve the rate of absorption and increase proteins, it is enough to carry out partial hydrolysis of the protein. As a result, the original molecule breaks down into chains of several amino acids, which are called di- and tri-peptides.
Protein hydrolysis process
At the end of the 19th century, scientists discovered that proteins consist of smaller particles called amino acids. And it was from that time that the study of both amino acids and methods of isolating them from the protein structure began. In which amino acids are not randomly linked, but are located in a specific DNA sequence. For the human body, this sequence does not matter. The body only needs amino acids, the task of which is to “extract” digestive system. During the digestion process, the body breaks down proteins into individual amino acids, which enter the blood. However, depending on hundreds of factors, digestion efficiency is far from 100%. Based on the percentage of substances absorbed during the digestion process, the nutritional value of a particular product is assessed. Hydrolysis can greatly increase the nutritional value of proteins. It is not opposed to such protein production processes as. Hydrolysis is the process of secondary processing of a protein that has already been isolated in one way or another.
The raw material for hydrolysis is already partially processed milk. As a rule, the cheapest milk protein is used. Considering the further processing and the end result, it makes no sense to take more expensive ingredients such as whey protein or isolate. For medical purposes, animal blood can also be used in hydrolysis, but it is not applicable in the sports industry. The main methods for hydrolyzing milk proteins are acid hydrolysis And enzymatic hydrolysis.
Acid hydrolysis
The essence of this process is the processing of raw materials with certain acids. The protein is treated with hydrochloric acid and heated to approximately 105-110 °C. It is kept in this state for 24 hours. As a result, molecular bonds are broken and proteins break down into individual amino acids. Acid hydrolysis is the simplest and cheapest to implement. However, he presents extremely high requirements to adherence to technology and, most importantly, to the quality and accuracy of reagent dosages. Using the wrong acids or incorrect dosages along with molecular bonds can destroy the amino acids themselves. As a result, the final product will have an incomplete amino acid spectrum. And the remains of salts and acids are unlikely to have a positive effect on digestion.
Enzymatic (enzymatic) hydrolysis
Enzymatic hydrolysis of proteins is somewhat similar natural process digestion. The starting material (usually -) is mixed with enzymes that carry out the “digestion” of protein and ensure its breakdown into amino acids. And it is this method that is most often used in the sports industry. Enzymatic (enzymatic) hydrolysis of proteins is less demanding in terms of technology. Excess enzymes are easier to remove and do not cause as much harm as acids.
At the first stage of enzymatic hydrolysis, the raw material is subjected to light heat treatment. As a result, the protein partially denatures (destroys). Then the resulting fraction is mixed with enzymes that complete the hydrolysis process.
The use of protein hydrolysis in sports nutrition
Protein hydrolysis is a real find and salvation for the industry. Thanks to it, you can not only obtain pure amino acid complexes, but also significantly increase the effectiveness of conventional proteins and gainers. Many even specially treat certain drugs with enzymes. As a result of this partial hydrolysis of the protein, its absorption rate increases. It also solves many problems with individual intolerance to milk protein components. On some products you can even find mention of the presence of digestive enzymes in them. In some proteins these are ordinary digestive enzymes that begin to work only in the stomach. And in some, these are the remnants of the enzymatic hydrolysis process. In any case, such proteins are absorbed much faster and better.
In theory, taking hydrolyzed protein can be replaced by taking simple protein in combination with digestive enzymes (such as festal, mezim forte, etc.). It will be significantly cheaper. However, taking milk protein and enzymes separately is not as effective. You'll never be able to pinpoint the right dosage enzymes. Their excess is unlikely to be beneficial to your body. Disadvantage: protein hydrolysis will be only partial.
The benefits and harms of protein hydrolysis
Protein hydrolysis is used in the following cases:
- To speed up protein absorption
- To reduce allergic reactions
- To obtain amino acids in their pure form
Particularly worth noting are the issues of allergic reactions. Food allergies It’s not uncommon these days; intolerance to foods or their individual components occurs quite regularly. An example is lactose intolerance. A food allergy is a reaction to specific proteins found in foods. When hydrolyzed, these proteins are broken down into peptides. Which are only fragments of proteins and no longer cause allergic reactions. It is especially worth noting that the nutritional value The resulting mixtures are in no way inferior to the nutritional value of the original raw materials.
Among the disadvantages of hydrolysis, it is worth noting the destruction beneficial bacteria. Despite the fact that many companies claim the presence of bifidobacteria, one must be objective - hydrolysis destroys them. And bifidobacteria can only be present when introduced from outside. However, if we are talking about sports nutrition, then in the first place here is still the nutritional value of the resulting mixture.
Squirrels- high molecular weight organic compounds, consisting of amino acid residues connected into a long chain by a peptide bond.
The composition of proteins in living organisms includes only 20 types of amino acids, all of which are alpha amino acids, and the amino acid composition of proteins and their order of connection with each other are determined by the individual genetic code of a living organism.
One of the features of proteins is their ability to spontaneously form spatial structures characteristic only of this particular protein.
Due to the specificity of their structure, proteins can have a variety of properties. For example, proteins having a globular quaternary structure, in particular protein chicken egg, dissolve in water to form colloidal solutions. Proteins with a fibrillar quaternary structure do not dissolve in water. Fibrillar proteins, in particular, form nails, hair, and cartilage.
Chemical properties of proteins
Hydrolysis
All proteins are capable of undergoing hydrolysis reactions. In the case of complete hydrolysis of proteins, a mixture of α-amino acids is formed:
Protein + nH 2 O => mixture of α-amino acids
Denaturation
The destruction of the secondary, tertiary and quaternary structures of a protein without destroying its primary structure is called denaturation. Protein denaturation can occur under the influence of solutions of sodium, potassium or ammonium salts - such denaturation is reversible:
Denaturation occurs under the influence of radiation (for example, heating) or treatment of the protein with salts heavy metals is irreversible:
For example, irreversible protein denaturation is observed during heat treatment of eggs during their preparation. As a result of denaturation of egg white, its ability to dissolve in water to form colloidal solution disappears.
Qualitative reactions to proteins
Biuret reaction
If a 10% sodium hydroxide solution is added to a solution containing protein, and then a small amount of a 1% copper sulfate solution, a violet color will appear.
protein solution + NaOH (10% solution) + CuSO 4 = purple color
Xanthoprotein reaction
Protein solutions turn yellow when boiled with concentrated nitric acid:
protein solution + HNO 3 (conc.) => yellow color
Biological functions of proteins
| catalytic | accelerate various chemical reactions in living organisms | enzymes |
| structural | cell building material | collagen, cell membrane proteins |
| protective | protect the body from infections | immunoglobulins, interferon |
| regulatory | regulate metabolic processes | hormones |
| transport | transfer of vital substances from one part of the body to another | hemoglobin carries oxygen |
| energy | supply the body with energy | 1 gram of protein can provide the body with 17.6 J of energy |
| motor (motor) | any motor functions of the body | myosin (muscle protein) |
Like other chemical reactions, protein hydrolysis is accompanied by the exchange of electrons between certain atoms of the reacting molecules. Without a catalyst, this exchange occurs so slowly that it cannot be measured. The process can be accelerated by adding acids or bases; The former give H-ions upon dissociation, the latter - OH-ions. Acids and bases play the role of true catalysts: they are not consumed during the reaction.
When protein is boiled with concentrated acid, it completely breaks down into free amino acids. If such a decay occurred in a living cell, it would naturally lead to its death. Under the influence of proterlytic enzymes, proteins also break down, and even faster, but without the slightest harm for the body. And while H ions act indiscriminately on all proteins and all peptide bonds in any protein, proteolytic enzymes are specific and only break certain bonds.
Proteolytic enzymes are themselves proteins. How does a proteolytic enzyme differ from a substrate protein (a substrate is a compound that is the target of the enzyme)? How does a proteolytic enzyme exhibit its catalytic activity without destroying itself or the cell? Answering these basic questions would help to understand the mechanism of action of all enzymes. Since M. Kunitz first isolated trypsin in crystalline form 30 years ago, proteolytic enzymes have served as models for studying the relationship between protein structure and enzymatic function.
Proteolytic enzymes of the digestive tract are associated with one of essential functions human body- assimilation nutrients. This is why these enzymes have long been the subject of research; in this respect, perhaps only the yeast enzymes involved in alcoholic fermentation are ahead of them. The best studied digestive enzymes are trypsin, chymotrypsin and carboxypeptidases (these enzymes are secreted by the pancreas). It is with their example that we will consider everything that is now known about the specificity, structure and nature of action of proteolytic enzymes.
Proteolytic enzymes of the pancreas are synthesized in the form of precursors - zymogens - and are stored in intracellular bodies, the so-called zymogen granules. Zymogens lack enzymatic activity and, therefore, cannot act destructively on the protein components of the tissue in which they are formed. Entering small intestine, zymogens are activated by another enzyme; at the same time, in the structure of their molecules there are small, but very important changes. We'll go into more detail about these changes later.
"Molecules and Cells", ed. G.M. Frank
