Last updated:2014.11.21.

Amino Acid Codes

Codes Used in Sequence Description

The amino acid code that is used with the International Nucleotide Sequence Database is as follows. These amino acids are described with one letter abbreviation in amino-acid sequence for the coding region.

The listed amino acid abbreviations are legal values for qualifiers /transl_except, /codon and /anticodon. Those that are not included in "Amino acid codes", please refer to Modified and Unusual Amino Acids.

Abbreviation 1 letter abbreviation Amino acid name
Ala A Alanine
Arg R Arginine
Asn N Asparagine
Asp D Aspartic acid
Cys C Cysteine
Gln Q Glutamine
Glu E Glutamic acid
Gly G Glycine
His H Histidine
Ile I Isoleucine
Leu L Leucine
Lys K Lysine
Met M Methionine
Phe F Phenylalanine
Pro P Proline
Pyl O Pyrrolysine
Ser S Serine
Sec U Selenocysteine
Thr T Threonine
Trp W Tryptophan
Tyr Y Tyrosine
Val V Valine
Asx B Aspartic acid or Asparagine
Glx Z Glutamic acid or Glutamine
Xaa X Any amino acid
Xle J Leucine or Isoleucine
TERM termination codon
IUPAC-IUB Joint Commission on Biochemical Nomenclature.Nomenclature and Symbolism for Amino Acids and Peptides.
Eur. J. Biochem. 138: 9-37 (1984).
Feature Table Definition: 7.4.3 Amino acid abbreviations