Loading Pathway...
Error: Pathway image not found.
Hide
Pathway Description
Tryptophan Metabolism
Homo sapiens
Metabolic Pathway
Created: 2013-08-19
Last Updated: 2023-10-25
This pathway depicts the metabolic reactions and pathways associated with tryptophan metabolism in animals. Tryptophan is an essential amino acid. This means that it cannot be synthesized by humans and other mammals and therefore must be part of the diet. Unlike animals, plants and microbes can synthesize tryptophan from shikimic acid or anthranilate. As one of the 20 proteogenic amino acids, tryptophan plays an important role in protein biosynthesis through the action of tryptophanyl-tRNA synthetase. As shown in this pathway, tryptophan can be linked to the tryptophanyl-tRNA via either the mitochondrial or cytoplasmic tryptophan tRNA ligases. Also shown in this pathway map is the conversion of tryptophan to serotonin (a neurotransmitter). In this process, tryptophan is acted upon by the enzyme tryptophan hydroxylase, which produces 5-hydroxytryptophan (5HTP). 5HTP is then converted into serotonin (5-HT) via aromatic amino acid decarboxylase. Serotonin, in turn, can be converted into N-acetyl serotonin (via serotonin-N-acetyltransferase) and then melatonin (a neurohormone), via 5-hydroxyindole-O-methyltransferase. The melatonin can be converted into 6-hydroxymelatonin via the action of cytochrome P450s in the endoplasmic reticulum. Serotonin has other fates as well. As depicted in this pathway it can be converted into N-methylserotonin via Indolethylamine-N-methyltransferase (INMT) or it can be converted into formyl-5-hydroxykynurenamine via indoleamine 2,3-dioxygenase. Serotonin may also be converted into 5-methoxyindoleacetate via a series of intermediates including 5-hydroxyindoleacetaldehyde and 5-hydroxyindoleacetic acid. Tryptophan can be converted or broken down into many other compounds as well. It can be converted into tryptamine via the action of aromatic amino acid decarboxylase. The resulting tryptamine can then be converted into indoleacetaldehyde via kynurenine 3-monooxygenase and then into indoleacetic acid via the action of aldehyde dehydrogenase. Tryptophan also leads to the production of a very important compound known as kynurenine. Kynurenine is synthesized via the action of tryptophan 2,3-dioxygnase, which produces N-formylkynurenine. This compound is converted into kynurenine via the enzyme known as kynurenine formamidase (AFMID). Kynurenine has at least 3 fates. First, kynurenine can undergo deamination in a standard transamination reaction yielding kynurenic acid. Secondly, kynurenine can undergo a series of catabolic reactions (involving kynureninase and kynurenine 3-monooxygenase) producing 3-hydroxyanthranilate plus alanine. In this reaction, kynureninase catabolizes the conversion of kynurenine into anthranilic acid while kynurenine—oxoglutarate transaminase (also known as kynurenine aminotransferase or glutamine transaminase K, GTK) catabolizes its conversion into kynurenic acid. The action of kynurenine 3-hydroxylase on kynurenic acid leads to 3-hydroxykynurenine. The oxidation of 3-hydroxyanthranilate converts it into 2-amino-3-carboxymuconic 6-semialdehyde, which has two fates. It can either degrade to form acetoacetate or it can cyclize to form quinolate. Most of the body’s 3-hydroxyanthranilate leads to the production of acetoacetate (a ketone body), which is why tryptophan is also known as a ketogenic amino acid. An important side reaction in the liver involves a non-enzymatic cyclization into quinolate followed by transamination and several rearrangements to yield limited amounts of nicotinic acid, which leads to the production of a small amount of NAD+ and NADP+.
References
Tryptophan Metabolism References
Lehninger, A.L. Lehninger principles of biochemistry (4th ed.) (2005). New York: W.H Freeman.
Salway, J.G. Metabolism at a glance (3rd ed.) (2004). Alden, Mass.: Blackwell Pub.
Badawy AA: Tryptophan metabolism, disposition and utilization in pregnancy. Biosci Rep. 2015 Sep 17;35(5). pii: BSR20150197. doi: 10.1042/BSR20150197.
Pubmed: 26381576
Bender DA: Biochemistry of tryptophan in health and disease. Mol Aspects Med. 1983;6(2):101-97.
Pubmed: 6371429
Hopkins FG, Cole SW: A contribution to the chemistry of proteids: Part II. The constitution of tryptophane, and the action of bacteria upon it. J Physiol. 1903 Jun 15;29(4-5):451-66. doi: 10.1113/jphysiol.1903.sp000968.
Pubmed: 16992682
Stavrum AK, Heiland I, Schuster S, Puntervoll P, Ziegler M: Model of tryptophan metabolism, readily scalable using tissue-specific gene expression data. J Biol Chem. 2013 Nov 29;288(48):34555-66. doi: 10.1074/jbc.M113.474908. Epub 2013 Oct 15.
Pubmed: 24129579
Hoglund E, Overli O, Andersson MA, Silva P, Laursen DC, Moltesen MM, Krogdahl A, Schjolden J, Winberg S, Vindas MA, Mayer I, Hillestad M: Dietary l-tryptophan leaves a lasting impression on the brain and the stress response. Br J Nutr. 2017 May;117(10):1351-1357. doi: 10.1017/S0007114517001428. Epub 2017 Jun 19.
Pubmed: 28625179
Li Y, Hu N, Yang D, Oxenkrug G, Yang Q: Regulating the balance between the kynurenine and serotonin pathways of tryptophan metabolism. FEBS J. 2017 Mar;284(6):948-966. doi: 10.1111/febs.14026. Epub 2017 Feb 20.
Pubmed: 28118532
Xu K, Liu H, Bai M, Gao J, Wu X, Yin Y: Redox Properties of Tryptophan Metabolism and the Concept of Tryptophan Use in Pregnancy. Int J Mol Sci. 2017 Jul 24;18(7). pii: ijms18071595. doi: 10.3390/ijms18071595.
Pubmed: 28737706
Smith SA, Pogson CL: Tryptophan and the control of plasma glucose concentrations in the rat. Biochem J. 1977 Dec 15;168(3):495-506. doi: 10.1042/bj1680495.
Pubmed: 147076
Theisen BE, Rumyantseva A, Cohen JS, Alcaraz WA, Shinde DN, Tang S, Srivastava S, Pevsner J, Trifunovic A, Fatemi A: Deficiency of WARS2, encoding mitochondrial tryptophanyl tRNA synthetase, causes severe infantile onset leukoencephalopathy. Am J Med Genet A. 2017 Sep;173(9):2505-2510. doi: 10.1002/ajmg.a.38339. Epub 2017 Jun 26.
Pubmed: 28650581
Wortmann SB, Timal S, Venselaar H, Wintjes LT, Kopajtich R, Feichtinger RG, Onnekink C, Muhlmeister M, Brandt U, Smeitink JA, Veltman JA, Sperl W, Lefeber D, Pruijn G, Stojanovic V, Freisinger P, V Spronsen F, Derks TG, Veenstra-Knol HE, Mayr JA, Rotig A, Tarnopolsky M, Prokisch H, Rodenburg RJ: Biallelic variants in WARS2 encoding mitochondrial tryptophanyl-tRNA synthase in six individuals with mitochondrial encephalopathy. Hum Mutat. 2017 Dec;38(12):1786-1795. doi: 10.1002/humu.23340. Epub 2017 Oct 6.
Pubmed: 28905505
Musante L, Puttmann L, Kahrizi K, Garshasbi M, Hu H, Stehr H, Lipkowitz B, Otto S, Jensen LR, Tzschach A, Jamali P, Wienker T, Najmabadi H, Ropers HH, Kuss AW: Mutations of the aminoacyl-tRNA-synthetases SARS and WARS2 are implicated in the etiology of autosomal recessive intellectual disability. Hum Mutat. 2017 Jun;38(6):621-636. doi: 10.1002/humu.23205. Epub 2017 Mar 23.
Pubmed: 28236339
Comings DE, Muhleman D, Dietz G, Sherman M, Forest GL: Sequence of human tryptophan 2,3-dioxygenase (TDO2): presence of a glucocorticoid response-like element composed of a GTT repeat and an intronic CCCCT repeat. Genomics. 1995 Sep 20;29(2):390-6. doi: 10.1006/geno.1995.9990.
Pubmed: 8666386
Ota T, Suzuki Y, Nishikawa T, Otsuki T, Sugiyama T, Irie R, Wakamatsu A, Hayashi K, Sato H, Nagai K, Kimura K, Makita H, Sekine M, Obayashi M, Nishi T, Shibahara T, Tanaka T, Ishii S, Yamamoto J, Saito K, Kawai Y, Isono Y, Nakamura Y, Nagahari K, Murakami K, Yasuda T, Iwayanagi T, Wagatsuma M, Shiratori A, Sudo H, Hosoiri T, Kaku Y, Kodaira H, Kondo H, Sugawara M, Takahashi M, Kanda K, Yokoi T, Furuya T, Kikkawa E, Omura Y, Abe K, Kamihara K, Katsuta N, Sato K, Tanikawa M, Yamazaki M, Ninomiya K, Ishibashi T, Yamashita H, Murakawa K, Fujimori K, Tanai H, Kimata M, Watanabe M, Hiraoka S, Chiba Y, Ishida S, Ono Y, Takiguchi S, Watanabe S, Yosida M, Hotuta T, Kusano J, Kanehori K, Takahashi-Fujii A, Hara H, Tanase TO, Nomura Y, Togiya S, Komai F, Hara R, Takeuchi K, Arita M, Imose N, Musashino K, Yuuki H, Oshima A, Sasaki N, Aotsuka S, Yoshikawa Y, Matsunawa H, Ichihara T, Shiohata N, Sano S, Moriya S, Momiyama H, Satoh N, Takami S, Terashima Y, Suzuki O, Nakagawa S, Senoh A, Mizoguchi H, Goto Y, Shimizu F, Wakebe H, Hishigaki H, Watanabe T, Sugiyama A, Takemoto M, Kawakami B, Yamazaki M, Watanabe K, Kumagai A, Itakura S, Fukuzumi Y, Fujimori Y, Komiyama M, Tashiro H, Tanigami A, Fujiwara T, Ono T, Yamada K, Fujii Y, Ozaki K, Hirao M, Ohmori Y, Kawabata A, Hikiji T, Kobatake N, Inagaki H, Ikema Y, Okamoto S, Okitani R, Kawakami T, Noguchi S, Itoh T, Shigeta K, Senba T, Matsumura K, Nakajima Y, Mizuno T, Morinaga M, Sasaki M, Togashi T, Oyama M, Hata H, Watanabe M, Komatsu T, Mizushima-Sugano J, Satoh T, Shirai Y, Takahashi Y, Nakagawa K, Okumura K, Nagase T, Nomura N, Kikuchi H, Masuho Y, Yamashita R, Nakai K, Yada T, Nakamura Y, Ohara O, Isogai T, Sugano S: Complete sequencing and characterization of 21,243 full-length human cDNAs. Nat Genet. 2004 Jan;36(1):40-5. doi: 10.1038/ng1285. Epub 2003 Dec 21.
Pubmed: 14702039
Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, Ko MS, Kawakami K, Suzuki Y, Sugano S, Gruber CE, Smith MR, Simmons B, Moore T, Waterman R, Johnson SL, Ruan Y, Wei CL, Mathavan S, Gunaratne PH, Wu J, Garcia AM, Hulyk SW, Fuh E, Yuan Y, Sneed A, Kowis C, Hodgson A, Muzny DM, McPherson J, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madari A, Young AC, Wetherby KD, Granite SJ, Kwong PN, Brinkley CP, Pearson RL, Bouffard GG, Blakesly RW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Griffith M, Griffith OL, Krzywinski MI, Liao N, Morin R, Palmquist D, Petrescu AS, Skalska U, Smailus DE, Stott JM, Schnerch A, Schein JE, Jones SJ, Holt RA, Baross A, Marra MA, Clifton S, Makowski KA, Bosak S, Malek J: The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome Res. 2004 Oct;14(10B):2121-7. doi: 10.1101/gr.2596504.
Pubmed: 15489334
Alberati-Giani D, Buchli R, Malherbe P, Broger C, Lang G, Kohler C, Lahm HW, Cesura AM: Isolation and expression of a cDNA clone encoding human kynureninase. Eur J Biochem. 1996 Jul 15;239(2):460-8. doi: 10.1111/j.1432-1033.1996.0460u.x.
Pubmed: 8706755
Toma S, Nakamura M, Tone S, Okuno E, Kido R, Breton J, Avanzi N, Cozzi L, Speciale C, Mostardini M, Gatti S, Benatti L: Cloning and recombinant expression of rat and human kynureninase. FEBS Lett. 1997 May 12;408(1):5-10. doi: 10.1016/s0014-5793(97)00374-8.
Pubmed: 9180257
Bechtel S, Rosenfelder H, Duda A, Schmidt CP, Ernst U, Wellenreuther R, Mehrle A, Schuster C, Bahr A, Blocker H, Heubner D, Hoerlein A, Michel G, Wedler H, Kohrer K, Ottenwalder B, Poustka A, Wiemann S, Schupp I: The full-ORF clone resource of the German cDNA Consortium. BMC Genomics. 2007 Oct 31;8:399. doi: 10.1186/1471-2164-8-399.
Pubmed: 17974005
Goh DL, Patel A, Thomas GH, Salomons GS, Schor DS, Jakobs C, Geraghty MT: Characterization of the human gene encoding alpha-aminoadipate aminotransferase (AADAT). Mol Genet Metab. 2002 Jul;76(3):172-80.
Pubmed: 12126930
Alberati-Giani D, Cesura AM, Broger C, Warren WD, Rover S, Malherbe P: Cloning and functional expression of human kynurenine 3-monooxygenase. FEBS Lett. 1997 Jun 30;410(2-3):407-12. doi: 10.1016/s0014-5793(97)00627-3.
Pubmed: 9237672
Breton J, Avanzi N, Magagnin S, Covini N, Magistrelli G, Cozzi L, Isacchi A: Functional characterization and mechanism of action of recombinant human kynurenine 3-hydroxylase. Eur J Biochem. 2000 Feb;267(4):1092-9. doi: 10.1046/j.1432-1327.2000.01104.x.
Pubmed: 10672018
Gregory SG, Barlow KF, McLay KE, Kaul R, Swarbreck D, Dunham A, Scott CE, Howe KL, Woodfine K, Spencer CC, Jones MC, Gillson C, Searle S, Zhou Y, Kokocinski F, McDonald L, Evans R, Phillips K, Atkinson A, Cooper R, Jones C, Hall RE, Andrews TD, Lloyd C, Ainscough R, Almeida JP, Ambrose KD, Anderson F, Andrew RW, Ashwell RI, Aubin K, Babbage AK, Bagguley CL, Bailey J, Beasley H, Bethel G, Bird CP, Bray-Allen S, Brown JY, Brown AJ, Buckley D, Burton J, Bye J, Carder C, Chapman JC, Clark SY, Clarke G, Clee C, Cobley V, Collier RE, Corby N, Coville GJ, Davies J, Deadman R, Dunn M, Earthrowl M, Ellington AG, Errington H, Frankish A, Frankland J, French L, Garner P, Garnett J, Gay L, Ghori MR, Gibson R, Gilby LM, Gillett W, Glithero RJ, Grafham DV, Griffiths C, Griffiths-Jones S, Grocock R, Hammond S, Harrison ES, Hart E, Haugen E, Heath PD, Holmes S, Holt K, Howden PJ, Hunt AR, Hunt SE, Hunter G, Isherwood J, James R, Johnson C, Johnson D, Joy A, Kay M, Kershaw JK, Kibukawa M, Kimberley AM, King A, Knights AJ, Lad H, Laird G, Lawlor S, Leongamornlert DA, Lloyd DM, Loveland J, Lovell J, Lush MJ, Lyne R, Martin S, Mashreghi-Mohammadi M, Matthews L, Matthews NS, McLaren S, Milne S, Mistry S, Moore MJ, Nickerson T, O'Dell CN, Oliver K, Palmeiri A, Palmer SA, Parker A, Patel D, Pearce AV, Peck AI, Pelan S, Phelps K, Phillimore BJ, Plumb R, Rajan J, Raymond C, Rouse G, Saenphimmachak C, Sehra HK, Sheridan E, Shownkeen R, Sims S, Skuce CD, Smith M, Steward C, Subramanian S, Sycamore N, Tracey A, Tromans A, Van Helmond Z, Wall M, Wallis JM, White S, Whitehead SL, Wilkinson JE, Willey DL, Williams H, Wilming L, Wray PW, Wu Z, Coulson A, Vaudin M, Sulston JE, Durbin R, Hubbard T, Wooster R, Dunham I, Carter NP, McVean G, Ross MT, Harrow J, Olson MV, Beck S, Rogers J, Bentley DR, Banerjee R, Bryant SP, Burford DC, Burrill WD, Clegg SM, Dhami P, Dovey O, Faulkner LM, Gribble SM, Langford CF, Pandian RD, Porter KM, Prigmore E: The DNA sequence and biological annotation of human chromosome 1. Nature. 2006 May 18;441(7091):315-21. doi: 10.1038/nature04727.
Pubmed: 16710414
Highlighted elements will appear in red.
Highlight Compounds
Highlight Proteins
Enter relative concentration values (without units). Elements will be highlighted in a color gradient where red = lowest concentration and green = highest concentration. For the best results, view the pathway in Black and White.
Visualize Compound Data
Visualize Protein Data
Settings