Histidine
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
| Image:Histidin - Histidine.svg Image:L-histidine-3D-sticks2.png | |
| Histidine | |
| Systematic (IUPAC) name | |
| 2-amino-3-(3H-imidazol-4-yl)propanoic acid | |
| Identifiers | |
| CAS number | 71-00-1 |
| PubChem | 773 |
| Chemical data | |
| Formula | C6H9N3O2 |
| Molar mass | 155.16 g/mol |
| SMILES | N[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 by German physician Albrecht Kossel in 1896.
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 slightly 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.
Because of histidine's affinity for metal ions, researchers will often add a polyhistidine-tag to a protein of interest. The metal affinity can then be used to purify, detect, or immobilize the protein to be studied.
Metabolism
The amino acid is a precursor for histamine and carnosine biosynthesis.
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 resonant.png
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
External links
- Histidine biosynthesis (early stages)
- Histidine biosynthesis (later stages)
- Histidine catabolism
- Computational Chemistry Wiki
| Major families of biochemicals | ||
| Peptides | Amino acids | Nucleic acids | Carbohydrates | Nucleotide sugars | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides | ||
| Analogues of nucleic acids: | The 20 Common Amino Acids ("dp" = data page) | Analogues 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) | ||
ca:Histidina cs:Histidin de:Histidineo:Histidino fr:Histidine ko:히스티딘 hr:Histidin id:Histidin it:Istidina he:היסטידין lv:Histidīns lb:Histidin lt:Histidinas hu:Hisztidin nl:Histidine ja:ヒスチジン no:Histidinfi:Histidiini sv:Histidinuk:Гістидин
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
