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Amino Acids

Basic Metabolism Top
Molecule Index
EC classes
( EC分類)
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Upper classes : BM Basic Metabolites


Class Overview

An amino acid has a carbon connected by an amino group and a carboxyl group (called an alpha carbon). Proteins are constituted from 20 amino acids.

Straight Class
 BMAAS2 (1 pages) Straight length 2
 BMAAS3 (19 pages) Straight length 3
Ser, Cys, Ala
 BMAAS4 (16 pages) Straight length 4
Asp, Asn, Thr
 BMAAS5 (16 pages) Straight length 5
Gln, Glu
 BMAAS6 (6 pages) Straight length 6
Branched Class
 BMAAB4 (2 pages) Branched length 4
Val, Met
 BMAAB5 (3 pages) Branched length 5
Arg, Leu, Ile
 BMAAB6 (0 pages) Branched length 6
Cyclic Class (click here to visit another page)

Physicochemical Characters

Character of amino acids
ID Code Symbol 構造 特徴 pI 必須アミノ酸?
L-Alanine Ala A -CH3 neutral 6.0
L-Serine Ser S -CH2OH neutral 5.7
L-Threonine Thr T -CH(OH)CH3 neutral 5.6 yes
L-Valine Val V -CH(CH3)2 neutral, branched 6.0 yes
L-Leucine Leu L -CH2CH(CH3)2 neutral, branched 6.0 yes
L-Isoleucine Ile I -CH(CH3)CH2CH3 neutral, branched 6.0 yes
L-Aspartate Asp D -CH2COOH acidic 2.8
L-Glutamate Glu E -CH2CH2COOH acidic 3.2
L-Asparagine Asn N -CH2CONH2 acidic, amido 5.4
L-Glutamine Gln Q -CH2CH2CONH2 acidic, amido 5.7
L-Lysine Lys K -(CH2)4NH3 basic 9.7 yes
L-Arginine Arg R -(CH2)3NHC(=NH)NH2 basic 10.8
L-Cysteine Cys C -CH2SH neutral, S 5.1
L-Methionine Met M -(CH2)2SCH3 neutral, S 5.7 yes
L-Phenylalanine Phe F -CH2-Benz neutral, aromatic 5.5 yes
L-Tyrosine Tyr Y -CH2-Benz-OH neutral, aromatic 5.7
L-Tryptophan Trp W -CH2-Indole neutral, aromatic 5.9 yes
L-Histidine His H -CH2-Imidazole basic, atomatic 7.6 yes
L-Proline Pro P -NH-(CH2)3- neutral, cyclic, 2nd amine 6.2

D and L in Amino Acid


Except for glycine, an amino acid contains a chiral carbon, distinguished by D or L (R or S). In the Fischer projection, which places the carboxyl group upward and amino acid-specific side-chain downward, the amino group must comes either left or right, protruding from the paper plane. If the hydrogen is left and amino group is right, the amino acid is called D, after D-glyceraldehide. If the amino group is left, it is called L.

D-glyceraldehyde.gif D-serine.gif L-serine.gif

DL and RS do not coincide

In the Cahn-Ingold-Prelog (or RS) notation, 19 L-amino acids become S-form (when H is placed behind the paper plane, the amino group, carboxyl group and side chain are arranged anticlockwise). Only L-cysteine becomes R-form because S in its side chain makes the arrangement in the different order: amino group, side chain, and carboxyl group. For this reason, although its tetrahedal configuration is the same as the rest of amino acids, it is R-form. Likewise, cystine is R-form too.

Glycine has no chiral carbon

Glycine has two Hydrogen branches and therefore not chiral. The amino group of proline is included in the ring sturucture and therefore secondary amine.

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