Table 1 - IUPAC Nomenclature

Nomenclature and Symbolism for Amino Acids and Peptides

Table 1. α-Amino acids incorporated into protein under mRNA direction.

This version of Table 1 does not use the HTML table format. In order to simulate a table layout subscripts are not used.

The systematic names and formulas given refer to hypothetical forms in which amino groups are unprotonated and carboxyl groups are undissociated. This convention is useful to avoid various nomenclatural problems but should not be taken to imply that these structures represent an appreciable fraction of the amino-acid molecules.

Trivial Symbols Systematic name (Note c) Formula (Note g) name (Note a) (Note b) Alanine Ala A 2-Aminopropanoic acid CH3-CH(NH2)-COOH Arginine Arg R 2-Amino-5-guanidinopentanoic H2N-C(=NH)-NH-[CH2]3-CH(NH2)-COOH acid Asparagine Asn N 2-Amino-3-carbamoylpropanoic H2N-CO-CH2-CH(NH2)-COOH (Note d) acid Aspartic acid Asp D 2-Aminobutanedioic acid HOOC-CH2-CH(NH2)-COOH (Note d) Cysteine Cys C 2-Amino-3-mercaptopropanoic HS-CH2-CH(NH2)-COOH acid Glutamine Gln Q 2-Amino-4-carbamoylbutanoic H2N-CO-[CH2]2-CH(NH2)-COOH (Note d) acid Glutamic acid Glu E 2-Aminopentanedioic acid HOOC-[CH2]2-CH(NH2)-COOH (Note d) Glycine Gly G Aminoethanoic acid CH2(NH2)-COOH Histidine His H 2-Amino-3-(1H-imidazol-4-yl)- propanoic acid Isoleucine Ile I 2-Amino-3-methylpentanoic C2H5-CH(CH3)-CH(NH2)-COOH acid (Note e) Leucine Leu L 2-Amino-4-methylpentanoic (CH3)2CH-CH2-CH(NH2)-COOH acid Lysine Lys K 2,6-Diaminohexanoic acid H2N-[CH2]4-CH(NH2)-COOH Methionine Met M 2-Amino-4-(methylthio)butanoic CH3-S-[CH2]2-CH(NH2)-COOH acid Phenylalanine Phe F 2-Amino-3-phenylpropanoic C6H5-CH2-CH(NH2)-COOH acid Proline Pro P Pyrrolidine-2-carboxylic acid Serine Ser S 2-Amino-3-hydroxypropanoic HO-CH2-CH(NH2)-COOH acid Threonine Thr T 2-Amino-3-hydroxybutanoic CH3-CH(OH)-CH(NH2)-COOH acid (Note e) Tryptophan Trp W 2-Amino-3-(lH-indol-3-yl)- propanoic acid Tyrosine Tyr Y 2-Amino-3-(4-hydroxyphenyl)- propanoic acid Valine Val V 2-Amino-3-methylbutanoic (CH3)2CH-CH(NH2)-COOH acid Unspecified Xaa X amino acid (Note f) a The trivial name refers to the L or D or DL-amino acid; for those that are chiral only the L-amino acid is used for protein biosynthesis.

b Use of the one-letter symbols should be restricted to the comparison of long sequences (3AA-20).

c The fully systematic forms ethanoic, propanoic, butanoic and pentanoic may alternatively be called acetic, propionic, butyric and valeric, respectively. Similarly, butanedioic = succinic, 3-carbamoylpropanoic = succinamic, pentanedioic = glutaric, and 4-carbamoylbutanoic = glutaramic.

d The symbol Asx denotes Asp or Asn; likewise B denotes N or D. Glx and Z likewise represent glutamic acid or glutamine or a substance, such as 4-carboxyglutamic acid, Gla (3AA-15.2.6), or 5-oxoproline, Glp (3AA-16.5), that yields glutamic acid on acid hydrolysis of peptides.

e See 3AA-3 and -4 for stereochemical designation.

f See Addendum for alternative use of X.

g All numbers should be subscripts in the Formula column. Where a graphic formula is used this may appear on the left on the next line.

Return to 3AA-1.