Histidine
C₆H₉N₃O₂·155.157 g/mol·Amino Acids·CID 773
Amino AcidEssential
The only amino acid whose imidazole side chain has a pKa (~6.0) near physiological pH, allowing it to act as both proton donor and acceptor. Essential for infants. Found in enzyme active sites where proton transfer is needed. Precursor to histamine.
IUPAC: 2-amino-3-(1H-imidazol-5-yl)propanoic acid
Also known as: 4998-57-6, 2-amino-3-(1H-imidazol-5-yl)propanoic acid, Histidine, DL-, QU6SDF3Q03, DL-2-Amino-3-(4-imidazolyl)propionsaeure (+14 more)
Molecular Structure
Molecular Propertiesmass · H-bonds · stereo
Molecular Weight
155.150g/mol
Exact Mass
155.069477Da
Monoisotopic Mass
155.069477Da
XLogP
-3.2
Polar Surface Area
92.0Ų
Complexity
151
Formal Charge
0
H-Bond Donors
3
H-Bond Acceptors
4
Rotatable Bonds
3
Heavy Atoms
11
Stereo Centers
0
Bond Stereo
0
Drug-Likeness (Lipinski's Rule of Five)
✓ 155.2 g/mol
MW ≤ 500
✓ -3.2
LogP ≤ 5
✓ 3
H-bond donors ≤ 5
✓ 4
H-bond acceptors ≤ 10
Passes all rules — good oral bioavailability predicted
Chemical IdentifiersSMILES · InChI
InChI
InChI=1S/C6H9N3O2/c7-5(6(10)11)1-4-2-8-3-9-4/h2-3,5H,1,7H2,(H,8,9)(H,10,11)
Constituent Elements
Isomers8 compounds with formula C₆H₉N₃O₂
(2S)-2-amino-3-(1H-imidazol-5-yl)propanoic acid
CID 6274 · 155.2 g/mol
(2S)-2-azaniumyl-3-(1H-imidazol-5-yl)propanoate
CID 6971009 · 155.2 g/mol
(2R)-2-amino-3-(1H-imidazol-5-yl)propanoic acid
CID 71083 · 155.2 g/mol
4,6-dimethoxypyrimidin-2-amine
CID 118946 · 155.2 g/mol
azanium N-oxido-N-phenylnitrous amide
CID 2724103 · 155.2 g/mol
ethyl 5-amino-1H-pyrazole-4-carboxylate
CID 81472 · 155.2 g/mol
6-amino-1,3-dimethylpyrimidine-2,4-dione
CID 81152 · 155.2 g/mol
2,6-dimethoxypyrimidin-4-amine
CID 76789 · 155.2 g/mol