Tryptophan hydroxylase

tryptophan 5-monooxygenase

Identifiers
EC number| 1.14.16.4
CAS number| 9037-21-2
Databases
IntEnz| IntEnz view
BRENDA| BRENDA entry
ExPASy| NiceZyme view
KEGG| KEGG entry
MetaCyc| metabolic pathway
PRIAM| profile
PDB structures| RCSB PDB PDBe PDBsum
Gene Ontology| AmiGO  / QuickGO
| Search

PMC| articles
PubMed| articles
NCBI| proteins
tryptophan hydroxylase 1 (tryptophan 5-monooxygenase)

Identifiers
Symbol| TPH1
Alt. symbols| TPRH, TPH
Entrez| 7166
HUGO| 12008
OMIM| 191060
PDB| 1MLW
RefSeq| NM_004179
UniProt| P17752
Other data
EC number| 1.14.16.4
Locus| Chr. 11 p15.3-p14
tryptophan hydroxylase 2

Identifiers
Symbol| TPH2
Entrez| 121278
HUGO| 20692
OMIM| 607478
RefSeq| NM_173353
UniProt| Q8IWU9
Other data
Locus| Chr. 12 q15

Tryptophan hydroxylase (TPH) is an enzyme (EC 1.14.16.4) involved in the synthesis of the neurotransmitter serotonin. Tyrosine hydroxylase, phenylalanine hydroxylase, and tryptophan hydroxylase together constitute the family of biopterin-dependent aromatic amino acid hydroxylases. TPH catalyzes the following chemical reaction

L-tryptophan \+ tetrahydrobiopterin \+ O2 <math>\rightleftharpoons</math> 5-Hydroxytryptophan \+ dihydrobiopterin \+ H2O

It employs one additional cofactor, iron.

## Contents

* 1 Function
* 2 Isoforms
* 3 Additional images
* 4 See also
* 5 References
* 6 Further reading
* 7 External links

## Function

[edit | edit source]

It is responsible for addition of the -HO group (hydroxylation) to the 5 position to form the amino acid 5-hydroxytryptophan (5-HTP), which is the initial and rate-limiting step in the synthesis of the neurotransmitter serotonin. It is also the first enzyme in the synthesis of melatonin.

Tryptophan hydroxylase (TPH), tyrosine hydroxylase (TH) and phenylalanine hydroxylase (PAH) are members of a superfamily of aromatic amino acid hydroxylases, catalyzing key steps in important metabolic pathways.[1] Analogously to phenylalanine hydroxylase and tyrosine hydroxylase, this enzyme uses (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) and dioxygen as cofactors.[2]

In humans, the stimulation of serotonin production by administration of tryptophan has an antidepressant effect[citation needed] and inhibition of tryptophan hydroxylase (e.g. by p-Chlorophenylalanine) may precipitate depression.[3]

The activity of tryptophan hydroxylase (i.e. the rate at which it converts L-tryptophan into the serotonin precursor L-5-hydroxytryptophan) can be increased when it undergoes phosphorylation. Protein Kinase A, for example, can phosphorylate tryptophan hydroxylase, thus increasing its activity.

## Isoforms

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In humans, as well as in other mammals, there are two distinct TPH genes. In humans, these genes are located on chromosomes 11 and 12 and encode two different homologous enzymes TPH1 and TPH2 (sequence identity 71%).[4]

* TPH1 is mostly expressed in tissues that express serotonin (a neurotransmitter) in the periphery (skin, gut, pineal gland) but it is also expressed in the central nervous system.
* On the other hand, TPH2 is exclusively expressed in neuronal cell types and is the predominant isoform in the central nervous system.

## Additional images

[edit | edit source]

* The pathway for the synthesis of serotonin from tryptophan

The pathway for the synthesis of serotonin from tryptophan

* Metabolic pathway from tryptophan to serotonin

Metabolic pathway from tryptophan to serotonin

## See also

[edit | edit source]

* Molecular and Cellular Biology portal

## References

[edit | edit source]

1. ↑ McKinney J, Teigen K, Frøystein NA, Salaün C, Knappskog PM, Haavik J, Martínez A (Dec 2001). "Conformation of the substrate and pterin cofactor bound to human tryptophan hydroxylase. Important role of Phe313 in substrate specificity" (PDF). Biochemistry. 40 (51): 15591–601. doi:10.1021/bi015722x. PMID 11747434. Archived from the original (PDF) on 2008-12-17.
2. ↑ "tetrahydrobiopterin". BH4 Databases. BH4.org. 2005. Archived from the original on 2006-12-06.
3. ↑ Wang L, Erlandsen H, Haavik J, Knappskog PM, Stevens RC (Oct 2002). "Three-dimensional structure of human tryptophan hydroxylase and its implications for the biosynthesis of the neurotransmitters serotonin and melatonin". Biochemistry. 41 (42): 12569–74. doi:10.1021/bi026561f. PMID 12379098.
4. ↑ Walther DJ, Bader M (Nov 2003). "A unique central tryptophan hydroxylase isoform". Biochemical Pharmacology. 66 (9): 1673–80. doi:10.1016/S0006-2952(03)00556-2. PMID 14563478.

## Further reading

[edit | edit source]

* Friedman PA, Kappelman AH, Kaufman S (Jul 1972). "Partial purification and characterization of tryptophan hydroxylase from rabbit hindbrain". The Journal of Biological Chemistry. 247 (13): 4165–73. PMID 4402511.
* Hamon M, Bourgoin S, Artaud F, Glowinski J (Nov 1979). "The role of intraneuronal 5-HT and of tryptophan hydroxylase activation in the control of 5-HT synthesis in rat brain slices incubated in K+-enriched medium". Journal of Neurochemistry. 33 (5): 1031–42. doi:10.1111/j.1471-4159.1979.tb05239.x. PMID 315449.
* Ichiyama A, Nakamura S, Nishizuka Y, Hayaishi O (Apr 1970). "Enzymic studies on the biosynthesis of serotonin in mammalian brain". The Journal of Biological Chemistry. 245 (7): 1699–709. PMID 5309585.
* Jequier E, Robinson DS, Lovenberg W, Sjoerdsma A (May 1969). "Further studies on tryptophan hydroxylase in rat brainstem and beef pineal". Biochemical Pharmacology. 18 (5): 1071–81. doi:10.1016/0006-2952(69)90111-7. PMID 5789774.
* Wang L, Erlandsen H, Haavik J, Knappskog PM, Stevens RC (Oct 2002). "Three-dimensional structure of human tryptophan hydroxylase and its implications for the biosynthesis of the neurotransmitters serotonin and melatonin". Biochemistry. 41 (42): 12569–74. doi:10.1021/bi026561f. PMID 12379098.
* Windahl MS, Petersen CR, Christensen HE, Harris P (Nov 2008). "Crystal structure of tryptophan hydroxylase with bound amino acid substrate". Biochemistry. 47 (46): 12087–94. doi:10.1021/bi8015263. PMID 18937498.

## External links

[edit | edit source]

* Tryptophan+Hydroxylase at the US National Library of Medicine Medical Subject Headings (MeSH)
* See also tryptophan hydroxylase in Proteopedia

* v
* t
* e

Enzymes involved in neurotransmission

monoamine|

| histidine → histamine|

| anabolism:|

* Histidine decarboxylase

|

catabolism:|

* Histamine N-methyltransferase
* Diamine oxidase

tyrosine→dopamine→epinephrine|

| anabolism:|

* Tyrosine hydroxylase
* Aromatic L-amino acid decarboxylase
* Dopamine beta-hydroxylase
* Phenylethanolamine N-methyltransferase

|

catabolism:|

* Catechol-O-methyl transferase
* Monoamine oxidase
* A
* B

glutamate→GABA|

| anabolism:|

* Glutamate decarboxylase

|

catabolism:|

* 4-aminobutyrate transaminase

tryptophan→serotonin→melatonin|

* Tryptophan hydroxylase
* Aromatic L-amino acid decarboxylase
* Aralkylamine N-acetyltransferase
* Acetylserotonin O-methyltransferase

arginine→NO|

* Nitric oxide synthase (NOS1, NOS2, NOS3)

choline→Acetylcholine|

| anabolism:|

* Choline acetyltransferase

|

catabolism:|

* Cholinesterase (Acetylcholinesterase, Butyrylcholinesterase)

* v
* t
* e

Oxidoreductases: dioxygenases, including steroid hydroxylases (EC 1.14)

1.14.11: 2-oxoglutarate|

* Prolyl hydroxylase
* Lysyl hydroxylase

1.14.13: NADH or NADPH|

* Flavin-containing monooxygenase
* FMO1
* FMO2
* FMO3
* FMO4
* FMO5
* Nitric oxide synthase
* NOS1
* NOS2
* NOS3
* Cholesterol 7 alpha-hydroxylase
* Methane monooxygenase
* 3A4
* Lanosterol 14 alpha-demethylase
* 24-hydroxycholesterol 7α-hydroxylase

1.14.14: reduced flavin or flavoprotein|

* 19A1
* 2D6
* 2E1

1.14.15: reduced iron-sulfur protein|

* 11B1
* 11B2
* 11A1

1.14.16: reduced pteridine (BH4 dependent)|

* Phenylalanine hydroxylase
* Tyrosine hydroxylase
* Tryptophan hydroxylase

1.14.17: reduced ascorbate|

* Dopamine beta-hydroxylase

1.14.18-19: other|

* Tyrosinase
* Stearoyl-CoA desaturase-1

1.14.99 \- miscellaneous|

* Cyclooxygenase
* Heme oxygenase (HMOX1)
* Squalene monooxygenase
* 17A1
* 21A2

* v
* t
* e

Enzymes

Activity|

* Active site
* Binding site
* Catalytic triad
* Oxyanion hole
* Enzyme promiscuity
* Catalytically perfect enzyme
* Coenzyme
* Cofactor
* Enzyme catalysis

Regulation|

* Allosteric regulation
* Cooperativity
* Enzyme inhibitor
* Enzyme activator

Classification|

* EC number
* Enzyme superfamily
* Enzyme family
* List of enzymes

Kinetics|

* Enzyme kinetics
* Eadie–Hofstee diagram
* Hanes–Woolf plot
* Lineweaver–Burk plot
* Michaelis–Menten kinetics

Types|

* EC1 Oxidoreductases (list)
* EC2 Transferases (list)
* EC3 Hydrolases (list)
* EC4 Lyases (list)
* EC5 Isomerases (list)
* EC6 Ligases (list)

* v
* t
* e

Monoamine metabolism modulators

Non-specific|

| AAAD|

* Substrates→Products: L-DOPA (levodopa)→Dopamine
* 5-HTP→Serotonin
* L-Histidine→Histamine
* Phenylalanine→Phenethylamine
* L-Tyrosine→Tyramine
* Tryptophan→Tryptamine

* Inhibitors: Benserazide
* Carbidopa
* DFMD
* Genistein
* Methyldopa

|

MAO|

* Substrates→Products (with ALDH/ALR): Epinephrine (adrenaline)→DHMA
* Metanephrine→MHPG/VMA
* Norepinephrine (noradrenaline)→DHMA
* Normetanephrine→MHPG/VMA
* Dopamine→DOPAC
* 3-Methoxytyramine→HVA
* Serotonin→5-HIAA

* Inhibitors: Non-selective: Benmoxin
* Caroxazone
* Echinopsidine
* Furazolidone
* Guineesine
* Hydralazine
* Indantadol
* Iproclozide
* Iproniazid
* Isocarboxazid
* Isoniazid
* Linezolid
* Mebanazine
* Metfendrazine
* Nialamide
* Octamoxin
* Paraxazone
* Phenelzine
* Pheniprazine
* Phenoxypropazine
* Pivhydrazine
* Procarbazine
* Safrazine
* Tranylcypromine

* Inhibitors: MAO-A-selective: Amiflamine
* Bazinaprine
* Befloxatone
* Brofaromine
* Cimoxatone
* Clorgiline
* CX157 (Tyrima)
* Eprobemide
* Esuprone
* Harmala alkaloids (e.g., harmine, harmaline, harman, norharman, tetrahydroharmine)
* Methylene blue
* Metralindole
* Minaprine
* Moclobemide
* Pirlindole
* Sercloremine
* Tetrindole
* Toloxatone

* Inhibitors: MAO-B selective: Adarigiline
* Almoxatone
* D-Deprenyl
* Ethanol
* Ladostigil
* Lazabemide
* Milacemide
* Mofegiline
* Nicotine
* Pargyline‡
* Rasagiline
* Safinamide
* Selegiline (L-Deprenyl)
* Sembragiline

Phenethylamines
(dopamine, epinephrine,
norepinephrine)|

| PAH|

* Substrates→Products: Phenylalanine→Tyrosine

* Inhibitors: 3,4-Dihydroxystyrene

|

TH|

* Substrates→Products: Tyrosine→L-DOPA (levodopa)

* Inhibitors: 2-Hydroxyestradiol
* 2-Hydroxyestrone
* 3-Iodotyrosine
* Aquayamycin
* Bulbocapnine
* Metirosine
* Oudenone

DBH|

* Substrates→Products: Dopamine→Norepinephrine (Noradrenaline)

* Inhibitors: Bupicomide
* Disulfiram
* Dopastin
* Fusaric acid
* Nepicastat
* Phenopicolinic acid
* Tropolone

PNMT|

* Substrates→Products: Norepinephrine (noradrenaline)→Epinephrine (adrenaline)

* Inhibitors: CGS-19281A
* SKF-64139
* SKF-7698

COMT|

* Substrates→Products: Dopamine→3-Methoxytyramine
* DOPAC→Homovanillic acid
* Norepinephrine→Normetanephrine
* Epinephrine→Metanephrine
* DOPEG→MOPEG
* DOMA→VMA
* 2-Hydroxyestradiol→2-Methoxyestradiol
* 2-Hydroxyestrone→2-Methoxyestrone
* 4-Hydroxyestradiol→4-Methoxyestradiol
* 4-Hydroxyestrone→4-Methoxyestrone

* Inhibitors: 2-Hydroxyestradiol
* 2-Hydroxyestrone
* Entacapone
* Nitecapone
* Opicapone
* Tolcapone

Tryptamines
(serotonin, melatonin)|

| TPH|

* Substrates→Products: Tryptophan→5-HTP

* Inhibitors: AGN-2979
* Fenclonine (PCPA)
* Telotristat ethyl

|

AANAT|

* Substrates→Products: Serotonin→N-Acetylserotonin

ASMT|

* Substrates→Products: N-Acetylserotonin→Melatonin

Histamine|

| HDC|

* Substrates→Products: L-Histidine→Histamine

* Inhibitors: Catechin
* Alpha-Fluoromethylhistidine
* Histidine methyl ester
* Meciadanol
* Naringenin
* Tritoqualine

|

HNMT|

* Substrates→Products: Histamine→N-Methylhistamine

* Inhibitors: Amodiaquine
* Diphenhydramine
* Harmaline
* Metoprine
* Quinacrine
* SKF-91488
* Tacrine

DAO|

* Substrates→Products: Histamine→Imidazole acetic acid

* Inhibitors: Pimagedine (aminoguanidine)

See also: Receptor/signaling modulators • Adrenergics • Dopaminergics • Melatonergics • Serotonergics • Monoamine reuptake inhibitors • Monoamine releasing agents • Monoamine neurotoxins

This EC 1.14 enzyme-related article is a stub. You can help Wikipedia by expanding it.

* v
* t
* e

*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template
*[AAAD]: Aromatic L-amino acid decarboxylase
*[MAO]: Monoamine oxidase
*[ALDH]: Aldehyde dehydrogenase
*[ALR]: Aldehyde reductase
*[PAH]: Phenylalanine hydroxylase
*[TH]: Tyrosine hydroxylase
*[DBH]: Dopamine beta-monooxygenase
*[PNMT]: Phenylethanolamine N-methyltransferase
*[COMT]: Catechol-O-methyl transferase
*[TPH]: Tryptophan hydroxylase
*[AANAT]: Serotonin N-acetyl transferase
*[ASMT]: Acetylserotonin O-methyltransferase
*[HDC]: Histidine decarboxylase
*[HNMT]: Histamine N-methyltransferase
*[DAO]: Diamine oxidase