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PBB Protein TPH1 image.jpg
Available structures
PDBOrtholog search: PDBe RCSB
AliasesTPH1, TPRH, TRPH, tryptophan hydroxylase 1
External IDsMGI: 98796 HomoloGene: 121565 GeneCards: TPH1
Gene location (Human)
Chromosome 11 (human)
Chr.Chromosome 11 (human)[1]
Chromosome 11 (human)
Genomic location for TPH1
Genomic location for TPH1
Band11p15.1Start18,017,564 bp[1]
End18,042,426 bp[1]
RNA expression pattern
PBB GE TPH1 214601 at fs.png
More reference expression data
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 11: 18.02 – 18.04 MbChr 7: 46.64 – 46.67 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Tryptophan hydroxylase 1 (TPH1) is an isoenzyme of tryptophan hydroxylase which in humans is encoded by the TPH1 gene.[5]

TPH1 was first discovered to synthesize serotonin in 1988[6] and was thought that there only was a single TPH gene until 2003, while a second form was found in the mouse (Tph2), rat and human brain (TPH2) and the original TPH was then renamed to TPH1.[7]


Tryptophan hydroxylases catalyze the biopterin-dependent monooxygenation of tryptophan to 5-hydroxytryptophan (5-HTP), which is subsequently decarboxylated to form the neurotransmitter serotonin (5-hydroxytryptamine or 5-HT). It is the rate-limiting enzyme in the biosynthesis of serotonin.

TPH expression is limited to a few specialized tissues: raphe neurons, pinealocytes, mast cells, mononuclear leukocytes, beta-cells of the islets of Langerhans, and intestinal and pancreatic enterochromaffin cells.[5][citation needed]

Clinical significance[edit]

Tryptophan hydroxylase is important for synthesizing indoleamine neurotransmitters and related compounds in the body and brain, including serotonin, melatonin, tryptamine, N-methyltryptamine, and N,N-dimethyltryptamine. TPH1 is expressed in the body, but not the brain.[7] Nevertheless, the effect of variations in the TPH1 gene on brain-related variables, such as personality traits and neuropsychiatric disorders, has been studied. For example, one study (1998) found an association between a polymorphism in the gene with impulsive-aggression measures,[8] while a case-control study (2001) could find no association between polymorphisms and Alzheimer's Disease.[9]

One human mutant of TPH1, A218C found in intron 7, is highly associated with schizophrenia.[10] Introns are regions of DNA that do not code for the amino acid sequence of a protein and were long considered to be 'junk DNA' lacking purpose. The correlation of an intron mutation with schizophrenia is significant because it suggests that introns have an important role in translation, transcription, or another, possibly unknown, aspect of the production of proteins from DNA.

See also[edit]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000129167 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000040046 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ a b "Entrez Gene: TPH1 tryptophan hydroxylase 1 (tryptophan 5-monooxygenase)".
  6. ^ Finocchiaro LM, Arzt ES, Fernández-Castelo S, Criscuolo M, Finkielman S, Nahmod VE (December 1988). "Serotonin and melatonin synthesis in peripheral blood mononuclear cells: stimulation by interferon-gamma as part of an immunomodulatory pathway". J. Interferon Res. 8 (6): 705–16. doi:10.1089/jir.1988.8.705. PMID 3148005.
  7. ^ a b Walther DJ, Peter JU, Bashammakh S, Hörtnagl H, Voits M, Fink H, Bader M (January 2003). "Synthesis of serotonin by a second tryptophan hydroxylase isoform". Science. 299 (5603): 76. doi:10.1126/science.1078197. PMID 12511643.
  8. ^ New AS, Gelernter J, Yovell Y, Trestman RL, Nielsen DA, Silverman J, Mitropoulou V, Siever LJ (1998). "Tryptophan hydroxylase genotype is associated with impulsive-aggression measures: a preliminary study". Am. J. Med. Genet. 81 (1): 13–7. doi:10.1002/(SICI)1096-8628(19980207)81:1<13::AID-AJMG3>3.0.CO;2-O. PMID 9514581.
  9. ^ Wang YC, Tsai SJ, Liu TY, Liu HC, Hong CJ (January 2001). "No association between tryptophan hydroxylase gene polymorphism and Alzheimer's disease". Neuropsychobiology. 43 (1): 1–4. doi:10.1159/000054856. PMID 11150890.
  10. ^ Allen NC, Bagade S, McQueen MB, Ioannidis JP, Kavvoura FK, Khoury MJ, Tanzi RE, Bertram L (July 2008). "Systematic meta-analyses and field synopsis of genetic association studies in schizophrenia: the SzGene database". Nat. Genet. 40 (7): 827–34. doi:10.1038/ng.171. PMID 18583979.

Further reading[edit]