Amino acids
Components and differences of amino acids
In a protein, the amino acids are strung together like a string of pearls. They belong to the class of organic compounds and consist of a carboxyl group and an amino group. The position of the amino group in relation to the carboxyl group indicates which group the respective class belongs to.
Alpha amino acids are amino acids that have a terminal carboxyl group and an amino group in the immediate vicinity.
Proteinogenic amino acids is a synonym for alpha amino acids and these are also the building blocks of proteins. The respective side chain of an amino acid distinguishes the amino acid of a class. The relevant side chain is also referred to as an amino acid residue or, in short, as a residue. If the residue differs from other substituents, then there is a stereocentre and there are two enantiomers of the respective amino acid. If the residue contains several stereocenters, then there are also diastereomers.
In order for the body to be able to utilise a dietary protein, this amino acid chain must be broken down using various digestive enzymes. We call the shorter fragments of proteins peptides (a combination of two to five amino acids).
The differences between amino acids
There are currently 22 known proteinogenic amino acids. The essential amino acids among them are
Phenylalanine
Threonine
Valine
Tryptophan
Isoleucine
Leucine
Lysine
Methionine
Other amino acids are "semi-essential". The BCAA amino acids (leucine, valine, isoleucine) known as dietary supplements also belong to the essential amino acids. The amino acid glutamine, like arginine, is a semi-essential amino acid.
Essential amino acids
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
Arginine and histidine are also essential for infants.
non-essential amino acids
- Glycine
- Alanine
- Serine
- Cysteine
- Tyrosine
- Proline
- Glutamic acid
- Glutamine
- Aspartic acid
- Asparagine
- Arginine (semi-essential)
- Histidine (semi-essential)
Amino acids exist in nature in a D- and an L-form. However, only the L-form occurs in proteinogenic amino acids. The D-amino acids are categorised as non-proteinogenic amino acids, d.h. these are amino acids that do not occur in proteins. Over 250 of these are known to date.
non-proteinogenic amino acids
- Citrulline
- Taurine
- Ornithine
from several amino acids and u.a. proteins formed in the metabolism
Glutathione or the therapeutically mainly relevant s-acetyl-glutathione
L-carnosine
