Tyrosine hydroxylase

Tyrosine hydroxylase

Constructed from 1toh
Identifiers
Symbols TH; DYT14; DYT5b; TYH
External IDs OMIM191290 MGI98735 HomoloGene307 GeneCards: TH Gene
EC number 1.14.16.2
RNA expression pattern
More reference expression data
Orthologs
Species Human Mouse
Entrez 7054 21823
Ensembl ENSG00000180176 ENSMUSG00000000214
UniProt P07101 Q3UTB3
RefSeq (mRNA) NM_000360.3 NM_009377.1
RefSeq (protein) NP_000351.2 NP_033403.1
Location (UCSC) Chr 11:
2.19 – 2.19 Mb
Chr 7:
150.08 – 150.12 Mb
PubMed search [1] [2]

Tyrosine hydroxylase or tyrosine 3-monooxygenase is the enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to dihydroxyphenylalanine (DOPA).[1][2] It does so using tetrahydrobiopterin as a coenzyme. DOPA is a precursor for dopamine, which, in turn, is a precursor for norepinephrine (noradrenaline) and epinephrine (adrenaline). In humans, tyrosine hydroxylase is encoded by the TH gene.[2]

Contents

Reaction

The enzyme, an oxygenase, is found in the cytosol of all cells containing catecholamines. This initial reaction is the rate limiting step in the production of catecholamines.

The enzyme is highly specific, not accepting indole derivatives - which is unusual as many other enzymes involved in the production of catecholamines do.


Clinical significance

Tyrosine hydroxylase can be inhibited by the drug α-methyl-para-tyrosine (Metirosine). This inhibition can lead to a depletion of dopamine and norepinepherine in the brain due to the lack of the precursor L-Dopa (L-3,4-dyhydroxyphenylalanine) which is synthesized by tyrosine hydroxylase. This drug is rarely used and can cause depression, but it is useful in treating pheochromocytoma and also resistant hypertension.


Tyrosine hydroxylase is an autoantigen in Autoimmune Polyendocrine Syndrome (APS) type I.[3]

Older examples of inhibitors mentioned in the literature include oudenone[4] and aquayamycin.[5]

Regulation

TH is increased acutely (minutes) by phosphorylation and chronically (days) by protein synthesis.[6] The phosphorylation can be sustained by nicotine for up to 48 hours.[7]

TH is decreased by the release of Catecholamines.

References

  1. ^ Kaufman S (1995). "Tyrosine hydroxylase". Adv. Enzymol. Relat. Areas Mol. Biol.. Advances in Enzymology - and Related Areas of Molecular Biology 70: 103–220. doi:10.1002/9780470123164.ch3. ISBN 9780470123164. PMID 8638482. 
  2. ^ a b Nagatsu T (1995). "Tyrosine hydroxylase: human isoforms, structure and regulation in physiology and pathology". Essays Biochem. 30: 15–35. PMID 8822146. 
  3. ^ Hedstrand H, Ekwall O, Haavik J, Landgren E, Betterle C, Perheentupa J, Gustafsson J, Husebye E, Rorsman F, Kämpe O (January 2000). "Identification of tyrosine hydroxylase as an autoantigen in autoimmune polyendocrine syndrome type I". Biochem. Biophys. Res. Commun. 267 (1): 456–61. doi:10.1006/bbrc.1999.1945. PMID 10623641. 
  4. ^ Ono M, Okamoto M, Kawabe N, Umezawa H, Takeuchi T (March 1971). "Oudenone, a novel tyrosine hydroxylase inhibitor from microbial origin". J. Am. Chem. Soc. 93 (5): 1285–6. doi:10.1021/ja00734a054. PMID 5545929. 
  5. ^ Ayukawa S, Takeuchi T, Sezaki M, Hara T, Umezawa H (May 1968). "Inhibition of tyrosine hydroxylase by aquayamycin". J. Antibiot. 21 (5): 350–3. PMID 5726288. 
  6. ^ http://www.mendeley.com/research/sustained-phosphorylation-tyrosine-hydroxylase-serine-40-novel-mechanism-maintenance-catecholamine-synthesis/
  7. ^ http://www.mendeley.com/research/sustained-phosphorylation-tyrosine-hydroxylase-serine-40-novel-mechanism-maintenance-catecholamine-synthesis/


Further reading

External links