The human organism cannot survive without proteins. They take over numerous functions in our body and are regarded as immensely important for the construction of cells. A protein is the essential basic building block of cells in the human body. This includes the muscles, the brain, the organs, the bones, the hair or even the nails. Without the supply of proteins, no cells are formed.
In technical literature, proteins are often regarded as natural macromolecules. They themselves require proteinogenic amino acids as building blocks. In this article, we show you how important and diverse these amino acids are as a crucial building block for proteins.
Proteins differ in their form
There are different types of proteins in this respect. Particularly striking is the diversity and the different fields of activity.
- Structural proteins can be found in all cell compartments. This is the designation of the different spaces of a cell. They serve as scaffolds in cells and tissues.
- Motor proteins ensure the intracellular transport of vesicles, which are important components for many processes within the cells.
- The so-called signal proteins transmit and receive information. These signals are transmitted from the cell membrane receptors to the cell nucleus.
- Enzyme proteins are also of great importance for the human organism. These act as a kind of biological catalyst and ensure smooth energy and building material metabolism.
- In addition, the so-called transport and storage proteins bind oxygen. This type of protein then transports the oxygen to exactly where it is needed.
Chemical characteristics as distinguishing features
A distinction is made between non-proteinogenic amino acids and proteinogenic amino acids.
Over 250 non-proteinogenic amino acids occur in our organism, although these cannot be detected in proteins. They are therefore considered to be non-protein-forming or non-proteinogenic.
The 22 so-called proteinogenic amino acids can produce proteins. In this respect, they are used in protein synthesis. Our body can produce most of these proteinogenic amino acids itself, the others we have to supply to our body.
The differences between the two are particularly evident in their respective chemical characteristics. In addition, proteins have different structures.
Proteinogenic amino acids are all linked together. This is a special form of binding known as peptide binding. This special bond can be formed because each acid in this form contains both an amino group and a carboxyl group.
Amino acid sequence – individual building plan for proteins
A proteinogenic amino acid is an organic carboxylic acid that has at least one amino group. Since the proteinogenic amino acid is responsible for the structure of proteins, there is an extremely high biological relevance here. The structure of proteins consists of peptidyl-linked amino acid building blocks with sequences of varying lengths. This special composition is called an amino acid sequence.
The sequence represents an individual characteristic for each individual protein, which acts as a personal blueprint. The number of linked amino acid building blocks varies from protein to protein. Some have several hundred building blocks, while other proteins even consist of more than 1,000 amino acid building blocks.
The muscle protein titin with its approximately 30,000 building blocks is considered the longest known protein. The amino acid sequence is correspondingly complex.
Classification into four different subgroups
A total of 21 proteinogenic amino acid variants are known today. The individual proteinogenic acids are divided into four categories:
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Polar side chains
Asparagine, cysteine, glutamine, selenocysteine, serine, threonine and tyrosine can be classified in this proteinogenic subgroup. From a chemical point of view, there is an uneven charge distribution in the molecules. From a medical point of view, polar side chains determine the alignment of the cells.
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Non-polar side chains
These include the proteinogenic amino acids alanine, glycine, isoleucine, leucine, methionine, proline, phenylalanine, tryptophan and valine. One amino acid from this group gives a protein hydrophobic properties. This means that proteins are not soluble in water, but in most cases, they are easily soluble in oil and fat. In this context, we also speak of lipophilia.
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Basic side chains
The amino acid versions arginine, histidine and lysine fall into this category. They have a so-called proton acceptor – a base – in the side chains and react basic in solutions. In most cases, they have an additional amino group.
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Acidic side chains
This subgroup contains only two proteinogenic amino acid versions, aspartate and glutamate. A special feature of these two acids is the proton donor present in the structure. This is a special substance that can transfer protons to an acid with a corresponding proton acceptor. This process is called protolysis.
Your body does not produce these proteinogenic amino acids
If the proteinogenic amino acids are not produced independently by the human body in sufficient quantities or not produced at all, a need arises. This is balanced out by taking the respective amino acids in your diet or via food supplements. A distinction is made between essential and semi-essential amino acids.
Your organism cannot produce the following eight acids itself. These are therefore called essential amino acids. Scientists and physicians have clearly defined what amounts of proteinogenic amino acids should be supplied to the body. The values are always per kilogram of weight and per day.
- Leucine: 10 to 50 milligrams (mg)
- Isoleucine: 20 mg
- Lysine: 30 to 64 mg
- phenylalanine: 38 to 52 mg
- Threonine: 16 mg
- Tryptophan: 4 mg
- methionine: 21 mg
- Valine: 26 mg
- Essential amino acids
Proteinogenic and semi-essential: arginine and histidine
In contrast, arginine and histidine belong to the semi-essential variants of the amino acid. Although the body synthesizes these substances, it may not synthesize them in sufficient quantities. Therefore, you should also take in these substances, which are important for the formation of proteins, additionally with food. With increasing age, the importance of these proteinogenic components for the cell structure and thus for your body increases.
They act as important tools to combat or contain stress and certain diseases. In addition, they also play a decisive role in targeted muscle building and muscle maintenance. The recommended daily amount per kilogram of weight for arginine is between one and five grams. For histidine, ten grams are given.
The protein development is not automatically guaranteed
The charge (positive or negative) plays an important role in the division into groups. Size and hydrophobicity are also important. Experiments have shown that not all amino acid variants defined as proteinogenic are really important for functional and reliable protein unfolding. This becomes clear from the events during evolution alone. At the beginning of the evolutionary chain, acids such as alanine and glycine first appeared.
These are extremely simply structured acids. Only later the complex structured, aromatic amino acid variants were added. Analyses of the structures suggest that tyrosine and tryptophane, for example, only entered the genetic code at a very late stage. And only after the lines of descent had already branched out.
Proteinogenic acids are involved in the formation of several substances in the body
As already described, amino acids identified as proteinogenic are important building blocks for proteins. These, in turn, are responsible for the formation and renewal of body cells. In addition, the acids contribute to covering the energy requirements of various processes in the body or organism. Some of the proteinogenic-oriented acids serve as messenger substances in the nervous system.
As starting substances, many amino acids are involved in the formation of important substances, such as messenger substances or hormones in the human body. Not to forget the positive influence on ornithine, y-aminobutyric acid and similar substances. This is because these amino acid variants that occur in the human body are formed directly from the acids defined as proteinogenic when required.
Also used in the food industry
To a small extent, proteinogenic acid versions are also contained as so-called free amino acids in a large number of different foods. These substances have a lasting effect on the taste. A typical example of such a scenario is the use of the special amino acid glutamine. The tasteless amino acid enhances the inherent taste of dishes and food by its own substance glutamate. An amino acid used in this form is irrelevant for the protein structure or for the formation of other substances.
We hope that our article has given you an overview of the function and importance of proteinogenic amino acids and that we have been able to give you a better understanding of their use. Try it yourself and convince yourself of their effect.