L-Histidine

Histidine was discovered in 1896 simultaneously by Albrecht Kossel and by Sven Hedin. Kossel first obtained it by precipitation with mercuric chloride from the alkaline solution containing the products of hydrolysis of the protamine, sturine. Hedin isolated it from the precipitate formed when the base fraction from hydrolyzed protein was treated with silver nitrate and then with ammonia until a maximum precipitation occurred.

IUPAC Name: (2S)-2-Amino-3-(3H-imidazol-4-yl)propanoic acid
Symbol: His or H
Molecular Weight: 155.15456 g/mol
Molecular Formula: C6H9N3O2
Canonical SMILES: C1=C(NC=N1)CC(C(=O)O)N
Isomeric SMILES: C1=C(NC=N1)C[C@@H](C(=O)O)N
InChIKey Identifier: HNDVDQJCIGZPNO-IFJFHIPQDC
CAS Number: 71-00-1
MDL Number: MFCD00064315
Melting point: 285 °C
Solubility in water: 41.6 g/1 L (25 °C)
2D Molfile: Get the molfile
3D PDB file: Get the PDB file
Other names: (S)-4-(2-Amino-2-carboxyethyl)imidazole ; (S)-alpha-Amino-1H-imidazole-4-propanoic acid; L-2-Amino-3-(4-imidazolyl)propionic acid; (2S)-2-azaniumyl-3-(3H-imidazol-4-yl)propanoate

Load 3D Structure of Histidine

L-Histidine is called a semi-essential amino acid because adults generally produce adequate amounts, but children may not. Histidine is a precursor of histamine, a compound released by the immune system cells during an allergic reaction.

The imidazole side chains and the relatively neutral pK of histidine (ca 6.0) mean that relatively small shifts in cellular pH will change its charge. For this reason, this amino acid side chain finds its way into considerable use as a co-ordinating ligand in metalloproteins, and also as a catalytic site in certain enzymes.

Go to Amino Acids index page.