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== Sequence and Structure ==
== Sequence and Structure ==
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Histidine Decarboxylase is considered to be a homo-dimer when one observe its [[biological assembly]]. A homo-dimer is a quaternary structure (link) formed by, usually non-covalently bound, identical monomers or protein chains. In human, three human HDC (hHDC) homo-dimers can be joined together to form a trimer [[asymmetric unit]]. <ref name=jbc/> <ref name=xray>PMID: 22684068<ref/>Thus, one can use the nomenclature “trimer of dimer” to suggest the complex might dissociate into smaller subunits before dissociating into monomers. The asymmetrical unit can be seen in Figure 1. Specifically, Cystein-180 and Cystein-418 are primary responsible for the oligomerization process of HDC. <ref name=xray/>
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Thus, one can use the nomenclature “trimer of dimer” to suggest the complex might dissociate into smaller subunits before dissociating into monomers. The asymmetrical unit can be seen in Figure 1. Specifically, Cystein-180 and Cystein-418 are primary responsible for the oligomerization process of HDC. <ref name=xray/>
== References ==
== References ==
{{reflist}}
{{reflist}}

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Histidine Decarboxylase

Histidine Decarboxylase (HDC) is an enzyme that is responsible for converting histamine from amino acid L-histidine. This enzyme belongs in the group II pyridoxal-5-phosphate (PLP)-dependent decarboxylase family. As the name suggested, this enzyme catalyzes the production of histamine by the removal of carboxylate group from the amino acid L-histidine whilst utilize pyridoxal phosphate as a cofactor. The mammalian Histamine decarboxylase is originated from HDC gene which encodes a 74kDa precursor polypeptide. However, the enzyme becomes active when its C-terminal is truncated into 54kDa during post-translation process. [1] [2] [3]

Contents


General Information

Histidine Decarboxylase

Symbol: HDC

Gene Name: HDC gene

Organism: Homo sapiens

Classification: Lyase

Length: 481 residues [4]

Chains: A, B, C, D, E, F [4]

Molecular Weight: 54314.8 kDa per chain [4]

Isoelectric Point: 5.4 (mouse HDC) [5] [2]

Km: 0.1 mM (human) [6] [7], 0.29mM (mouse stomach) [5], 0.26mM (mouse mastocytoma P-815 cells) [2]

Vmax: 1880 nmol/min/mg

Asymmetrical unit of Histidine Decarboxylase bound to 3 substrate analogs Histidine methyl ester (HME)

Drag the structure with the mouse to rotate

Sequence and Structure

Thus, one can use the nomenclature “trimer of dimer” to suggest the complex might dissociate into smaller subunits before dissociating into monomers. The asymmetrical unit can be seen in Figure 1. Specifically, Cystein-180 and Cystein-418 are primary responsible for the oligomerization process of HDC. [8]


References

  1. ↑ Taguchi Y, Watanabe T, Kubota H, Hayashi H, Wada H. Purification of histidine decarboxylase from the liver of fetal rats and its immunochemical and immunohistochemical characterization. J Biol Chem. 1984 Apr 25;259(8):5214-21. PMID:6425286
  2. ↑ 2.0 2.1 2.2 Ohmori E, Fukui T, Imanishi N, Yatsunami K, Ichikawa A. Purification and characterization of l-histidine decarboxylase from mouse mastocytoma P-815 cells. J Biochem. 1990 Jun;107(6):834-9. PMID:2118138
  3. ↑ Schwelberger, Hubert G. "Metabolism of Histamine." European Histamine Research Society Nov. 2013. Web. 29 Nov. 2013. http://www.ehrs.org.uk/schwelberger.pdf
  4. ↑ 4.0 4.1 4.2 "Human Histidine Decarboxylase Complex with Histidine Methyl Ester (HME)." RSCB Protein Data Bank. RCSB. Web. 29 Nov. 2013. <http://www.rcsb.org/pdb/explore/explore.do?structureId=4E1O>.
  5. ↑ 5.0 5.1 Watabe A, Fukui T, Ohmori E, Ichikawa A. Purification and properties of L-histidine decarboxylase from mouse stomach. Biochem Pharmacol. 1992 Feb 4;43(3):587-93. PMID:1540215
  6. ↑ Komori H, Nitta Y, Ueno H, Higuchi Y. Structural study reveals Ser345 determines substrate specificity on human histidine decarboxylase. J Biol Chem. 2012 Jul 5. PMID:22767596 doi:10.1074/jbc.M112.381897
  7. ↑ "P19113 (DCHS_HUMAN)." UniProt. Protein Knowledgebase. Web. 29 Nov. 2013 <http://www.uniprot.org/uniprot/P19113>.
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named xray
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