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Information about Histidine




Histidine

Systematic (IUPAC) name
2-amino-3-(3H-imidazol-4-yl)propanoic acid
Identifiers
CAS number71-00-1
PubChem        773
Chemical data
FormulaC6H9N3O2 
Mol. weight155.16 g/mol
SMILESN[C@@H](Cc1[nH]cnc1)C(O)=O
Complete data


Histidine (abbreviated as His or H)[1] is one of the 20 most common natural amino acids present in proteins. In the nutritional sense, in humans, histidine is considered an essential amino acid, but mostly only in children. Its codons are CAU and CAC.

Histidine was first isolated in 1896 by German physician Albrecht Kossel.

Chemical properties

The imidazole side chains and the relatively neutral pKa 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 coordinating ligand in metalloproteins, and also as a catalytic site in certain enzymes. The imidazole side chain has two nitrogens with different properties: One is bound to hydrogen and donates its lone pair to the aromatic ring and as such is slighty acidic, whereas the other one donates only one electron pair to the ring so it has a free lone pair and is basic. These properties are exploited in different ways in proteins. In catalytic triads, the basic nitrogen of histidine is used to abstract a proton from serine, threonine or cysteine to activate it as a nucleophile. In a histidine proton shuttle, histidine is used to quickly shuttle protons, it can do this by abstracting a proton with its basic nitrogen to make a positively-charged intermediate and then use another molecule, a buffer, to extract the proton from its acidic nitrogen. In carbonic anhydrases, a histidine proton shuttle is utilized to rapidly shuttle protons away from a zinc-bound water molecule to quickly regenerate the active form of the enzyme.

Metabolism

The amino acid is a precursor for histamine and carnosine biosynthesis.

Enlarge picture
Conversion of histidine to histamine by histidine decarboxylase


The enzyme histidine ammonia-lyase converts histidine into ammonia and urocanic acid. A deficiency in this enzyme is present in the rare metabolic disorder histidinemia.

Additional images


Histidine

The histidine bound heme group of succinate dehydrogenase, an electron carrier in the mitochondrial electron transfer chain. The large semi-transparent sphere indicates the location of the iron ion. From PDB 1YQ3.


References

1. ^ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature. Nomenclature and Symbolism for Amino Acids and Peptides. Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc. Retrieved on 2007-05-17.

External links


 •  • [ e]
Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids:The 20 Common Amino AcidsAnalogues of nucleic acids:
Alanine (dp) | Arginine (dp) | Asparagine (dp) | Aspartic acid (dp) | Cysteine (dp) | Glutamic acid (dp) | Glutamine (dp) | Glycine (dp) | Histidine (dp) | Isoleucine (dp) | Leucine (dp) | Lysine (dp) | Methionine (dp) | Phenylalanine (dp) | Proline (dp) | Serine (dp) | Threonine (dp) | Tryptophan (dp) | Tyrosine (dp) | Valine (dp)
IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. It is developed and kept up to date under the auspices of the International Union of Pure and Applied Chemistry (IUPAC).
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CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. They are also referred to as CAS numbers, CAS RNs or CAS #s.
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PubChem is a database of chemical molecules. The system is maintained by the National Center for Biotechnology Information (NCBI), a component of the National Library of Medicine, which is part of the United States National Institutes of Health (NIH).
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A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
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4, 2
(mildly acidic oxide)
Electronegativity 2.55 (Pauling scale)
Ionization energies
(more) 1st: 1086.5 kJmol−1
2nd: 2352.6 kJmol−1
3rd: 4620.5 kJmol−1

Atomic radius 70 pm
Atomic radius (calc.
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1, −1
(amphoteric oxide)
Electronegativity 2.20 (Pauling scale) More

Atomic radius 25 pm
Atomic radius (calc.) 53 pm
Covalent radius 37 pm
Van der Waals radius 120 pm
Miscellaneous

Thermal conductivity (300 K) 180.
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3, 5, 4, 2
(strongly acidic oxide)
Electronegativity 3.04 (Pauling scale)
Ionization energies
(more) 1st: 1402.3 kJmol−1
2nd: 2856 kJmol−1
3rd: 4578.1 kJmol−1

Atomic radius 65 pm
Atomic radius (calc.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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molecular mass (abbreviated Mr) of a substance, formerly also called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12).
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smiles

File extension: .smi
Type of format: chemical file format

The simplified molecular input line entry specification or SMILES
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The complete data for Histidine

General information

Chemical formula: C

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amino acid is a molecule that contains both amine and carboxyl functional groups. In biochemistry, this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent.
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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Nutrition is a science that examines the relationship between diet and health. Dietitians are health professionals who specialize in this area of study, and are trained to provide safe, evidence-based dietary advice and interventions.
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An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet.

Essentiality vs.


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Ludwig Karl Martin Leonhard Albrecht Kossel (September 16, 1853 – July 5, 1927) was a German medical doctor.

Biography

Kossel was born in Rostock as the son of Prussian consul Albrecht Kossel and his wife Clara.
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Imidazole is a heterocyclic aromatic organic compound. It is further classified as an alkaloid. Imidazole refers to the parent compound C3H4N2, whereas imidazoles are a class of heterocycles with similar ring structure but varying substituents.
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side chain in organic chemistry and biochemistry is a part of a molecule that is attached to a core structure. An R group is a generic label for a side chain which can be anything; however, it is typically stable and covalently linked to the adjoining atom.
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    pH is a measure of the acidity or alkalinity of a solution. Aqueous solutions at 25 ℃ with a pH less than seven are considered acidic, while those with a pH greater than seven are considered basic (alkaline). The pH of 7.
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    In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as
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    In biochemistry, a metalloprotein is a generic term for a protein that contains a metal cofactor. The metal may be an isolated ion or may be coordinated with a nonprotein organic compound, such as the porphyrin found in hemoproteins.
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    catalysis is the acceleration (increase in rate) of a chemical reaction by means of a substance called a catalyst, which is itself not consumed by the overall reaction.
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    Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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    ACID (Atomicity, Consistency, Isolation, Durability) is a set of properties that guarantee that database transactions are processed reliably. In the context of databases, a single logical operation on the data is called a transaction.
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      In chemistry, a base is most commonly thought of as a substance that can accept protons. This refers to the Brønsted-Lowry theory of acids and bases. Alternate definitions of bases include electron pair donors (Lewis), and as sources of hydroxide anions (Arrhenius).
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      A catalytic triad commonly refers to the three amino acid residues found inside the active site of certain protease enzymes: serine (S), aspartate (D) and histidine (H). They work together to break peptide bonds on polypeptides.
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      Serine (abbreviated as Ser or S)[1] is an organic compound with the formula HO2CCH(NH2)CH2OH. It is one of the 20 naturally occurring proteinogenic amino acids. Its codons are UCU, UCC, UCA, UCG, AGU and AGC.
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      Threonine (abbreviated as Thr or T)[1] is an α-amino acid with the chemical formula HO2CCH(NH2)CH(OH)CH3. Its codons are ACU and ACA. This essential amino acid is classified as polar.
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      Cysteine (abbreviated as Cys or C)[1] is an α-amino acid with the chemical formula HO2CCH(NH2)CH2SH. It is not an essential amino acid, which means that humans can synthesize it. Its codons are UGU and UGC.
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      In chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a reagent that forms a chemical bond to its reaction partner (the electrophile) by donating both bonding electrons.
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