Peptide Nomenclature Guide

Symbols and structures for amino acids

Common (“proteinogenic” or “coded”) amino acids have a three-letter symbol and are also represented by a one-letter symbol. Uncommon amino acids also have three-letter symbols and can be represented by the one-letter symbol “X”. The tables below list the symbols and abbreviations used in our website and literature.

Table 1. Common Amino Acids
Table 2. Uncommon Amino Acids
Table 3. Substituents

Table 1. Common Amino Acids

Key - Acidic Basic Non-polar (hydrophobic) Polar (uncharged)

Amino acid	Three-letter symbol	One-letter symbol	Chemical structure

Alanine	Ala	A
Arginine	Arg	R
Asparagine	Asn	N
Aspartic acid	Asp	D
Cysteine	Cys	C
Glutamine	Gln	Q
Glutamic acid	Glu	E
Glycine	Gly	G
Histidine	His	H
Isoleucine	Ile	I
Leucine	Leu	L
Lysine	Lys	K
Methionine	Met	M
Phenylalanine	Phe	F
Proline	Pro	P
Serine	Ser	S
Threonine	Thr	T
Tryptophan	Trp	W
Tyrosine	Tyr	Y
Valine	Val	V

Table 2. Uncommon Amino Acids

Three letter symbol	Amino Acid

Aad	2-Aminoadipic acid (2-aminohexanedioic acid)
Aan	α-Asparagine
Abu	2-Aminobutanoic acid
Aca	2-Aminocapric acid (2-aminodecanoic acid)
Agn	α-Glutamine
Aib	α-Aminoisobutyric acid (α-methylalanine)
Apm	2-Aminopimelic acid (2-aminoheptanedioic acid)
App	γ-Amino-β-hydroxybenzenepentanoic acid
Asu	2-Aminosuberic acid (2-aminooctanedioic acid)
Aze	2-Carboxyazetidine
Bal	β-Alanine
Bas	β-Aspartic acid
Bly	3,6-Diaminohexanoic acid (β-lysine)
Bua	Butanoic acid
Bux	4-Amino-3-hydroxybutanoic acid
Cap	γ-Amino-β-hydroxycyclohexanepentanoic acid
Cha	3-Cyclohexylalanine
Cit	N⁵-Aminocarbonylornithine
Cya	3-Sulfoalanine
Dab	2,4-Diaminobutanoic acid
Dap	Diaminopropionic acid
Dpm	Diaminopimelic acid
Dpr	2,3-Diaminopropanoic acid
Dsu	2,7-Diaminosuberic acid (2,7-diaminooctanedioic acid)
Edc	S-Ethylthiocysteine
Ggu	γ-Glutamic acid
Gla	γ-Carboxyglutamic acid
Glc	Hydroxyacetic acid (glycolic acid)
Glp	Pyroglutamic acid (Pyr) (pGlu)
Har	Homoarginine
Hcy	Homocysteine
Hhs	Homohistidine
Hiv	2-Hydroxyisovaleric acid
Hse	Homoserine
Hva	2-Hydroxypentanoic acid
Hyl	5-Hydroxylysine
Hyp	4-Hydroxyproline
Igl	α-Amino-2-indanacetic acid
Iva	Isovaline
Lac	2-Hydroxypropanoic acid (lactic acid)
Maa	Mercaptoacetic acid
Mba	Mercaptobutanoic acid
Mhp	3-Hydroxy-4-methylproline
Mpa	Mercaptopropanoic acid
Nal	3-Naphthylalanine
Nle	Norleucine
Nphe	N-Benzylglycine
Nty	Nortyrosine
Nva	Norvaline
Oaa	ω-Amino acid
Oic	2-Carboxyoctahydroindole
Orn	Ornithine
Pen	Penicillamine (3-mercaptovaline)
Phg	2-Phenylglycine
Pip	2-Carboxypiperidine
pSer	Phospho-L-serine
pThr	Phospho-L-threonine
pTyr	Phospho-L-tyrosine
Sar	Sarcosine (N-methylglycine)
Spg	1-Amino-1-carboxycyclopentane
Sta	Statin (4-amino-3-hydroxy-6-methylheptanoic acid)
Thi	3-Thienylalanine
Tic	3-Carboxyisoquinoline
Tle	3-Methylvaline
Tml	ε-N-Trimethyllysine
Tza	3-Thiazolylalanine
Und	Undefined
Wil	α-Amino-2,4-dioxopyrimidinepropanoic acid

Table 3. Substituents

Abbreviation	Substituent

Ac	Acetyl
Bn	Benzyl, Bzl
Bz	Benzoyl
For	Formyl
Me	Methyl
Myr	Myristoyl
Z	Benzyloxycarbonyl

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