Proteinogenic

Proteinogenic amino acids are those amino acids that are incorporated biosynthetically into proteins during translation. The word "proteinogenic" means "protein creating". Throughout known life, there are 22 genetically encoded (proteinogenic) amino acids, 20 in the standard genetic code and an additional 2 that can be incorporated by special translation mechanisms.

Overview

The 22 proteinogenic amino acids are found in genetic code. They are encoded by the standard genetic code. The genetic code is a set of three-nucleotide sets called codons. Each codon corresponds to a specific amino acid, or to a stop signal during protein synthesis.

Classification

Proteinogenic amino acids can be classified according to a variety of schemes, including their physical properties, metabolic pathways, and more.

By properties

• Aliphatic: Glycine, Alanine, Valine, Leucine, Isoleucine, Proline
• Aromatic: Phenylalanine, Tyrosine, Tryptophan
• Polar: Serine, Threonine, Cysteine, Tyrosine, Asparagine, Glutamine
• Acidic: Aspartic acid, Glutamic acid
• Basic: Arginine, Lysine, Histidine

By metabolic pathways

• Glycolytic: Glycine, Alanine, Serine, Cysteine, Tryptophan
• Citric acid cycle (Krebs cycle): Aspartic acid, Asparagine, Glutamic acid, Glutamine, Proline, Arginine
• Pentose phosphate pathway: Glycine, Serine, Tyrosine, Phenylalanine

Non-proteinogenic amino acids

In addition to the 22 proteinogenic amino acids, there are many non-proteinogenic amino acids. Non-proteinogenic amino acids are not found in proteins, but are significant in the biosynthesis of proteins.

See also

• Amino acid
• Protein (nutrient)
• Translation (biology)

References

Proteinogenic Resources
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