11.4 g/L at 25 °C,
17.1 g/L at 50 °C,
27.95 g/L at 75 °C
Solubility
Soluble in hot alcohol, alkali hydroxides; insoluble in chloroform.
Acidity (pKa)
2.38 (carboxyl), 9.39 (amino)[2]
Magnetic susceptibility (χ)
-132.0·10−6 cm3/mol
Pharmacology
ATC code
N06AX02 (WHO)
Supplementary data page
Tryptophan (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Chemical compound
Tryptophan (symbol Trp or W)[3]
is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic beta carbon substituent. Tryptophan is also a precursor to the neurotransmitter serotonin, the hormone melatonin, and vitamin B3.[4] It is encoded by the codon UGG.
Like other amino acids, tryptophan is a zwitterion at physiological pH where the amino group is protonated (–NH+ 3; pKa = 9.39) and the carboxylic acid is deprotonated ( –COO−; pKa = 2.38).[5]
Humans and many animals cannot synthesize tryptophan: they need to obtain it through their diet, making it an essential amino acid. In 2023, the emission spectrum of tryptophan was discovered in the interstellar gas of the star cluster IC 348.[6]
Tryptophan is named after the digestive enzymes trypsin, which were used in its first isolation from casein proteins.[7] It was assigned the one-letter symbol W based on the double ring being visually suggestive to the bulky letter.[8]
^ abGörbitz CH, Törnroos KW, Day GM (2012). "Single-crystal investigation of L-tryptophan with Z′ = 16". Acta Crystallogr. B. 68 (Pt 5): 549–557. doi:10.1107/S0108768112033484. PMID 22992800.
^Dawson RM, et al. (1969). Data for Biochemical Research. Oxford: Clarendon Press. ISBN 0-19-855338-2.
^
"Nomenclature and Symbolism for Amino Acids and Peptides". IUPAC-IUB Joint Commission on Biochemical Nomenclature. 1983. Archived from the original on 2 December 2021. Retrieved 22 October 2022.
^Slominski A, Semak I, Pisarchik A, Sweatman T, Szczesniewski A, Wortsman J (2002). "Conversion of L-tryptophan to serotonin and melatonin in human melanoma cells". FEBS Letters. 511 (1–3): 102–6. doi:10.1016/s0014-5793(01)03319-1. PMID 11821057. S2CID 7820568.
^"L-tryptophan | C11H12N2O2 - PubChem". pubchem.ncbi.nlm.nih.gov. Retrieved 22 December 2016.
^Iglesias-Groth S (August 2023). "A search for tryptophan in the gas of the IC 348 star cluster of the Perseus molecular cloud". Monthly Notices of the Royal Astronomical Society. 523 (2): 2876–2886. Bibcode:2023MNRAS.523.2876I. doi:10.1093/mnras/stad1535.
^Curzon G (31 December 1987), Bender DA, Joseph MH, Kochen W, Steinhart H (eds.), "Hopkins and the Discovery of Tryptophan", Progress in Tryptophan and Serotonin Research 1986, Berlin, Boston: De Gruyter, pp. XXIX–XL, doi:10.1515/9783110854657-004, ISBN 978-3-11-085465-7, retrieved 19 February 2024
^"IUPAC-IUB Commission on Biochemical Nomenclature A One-Letter Notation for Amino Acid Sequences". Journal of Biological Chemistry. 243 (13): 3557–3559. 10 July 1968. doi:10.1016/S0021-9258(19)34176-6.
Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid...
Tryptophan repressor (or trp repressor) is a transcription factor involved in controlling amino acid metabolism. It has been best studied in Escherichia...
Tryptophan synthase or tryptophan synthetase is an enzyme (EC 4.2.1.20) that catalyses the final two steps in the biosynthesis of tryptophan. It is commonly...
bacteria. The operon is regulated so that, when tryptophan is present in the environment, the genes for tryptophan synthesis are repressed. The trp operon contains...
Tryptophan hydroxylase (TPH) is an enzyme (EC 1.14.16.4) involved in the synthesis of the monoamine neurotransmitter serotonin. Tyrosine hydroxylase, phenylalanine...
In addition, tryptophan is a relatively rare amino acid; many proteins contain only one or a few tryptophan residues. Therefore, tryptophan fluorescence...
enzymology, a tryptophan dimethylallyltransferase (EC 2.5.1.34) is an enzyme that catalyzes the chemical reaction dimethylallyl diphosphate + L-tryptophan ⇌ {\displaystyle...
Tryptophan hydroxylase 1 (TPH1) is an isoenzyme of tryptophan hydroxylase which in humans is encoded by the TPH1 gene. TPH1 was first discovered to support...
but not uptake of tryptophan. This lowers the ratio of these branched-chain amino acids in the bloodstream relative to tryptophan (an aromatic amino...
Acute tryptophan depletion (ATD) is a technique used extensively to study the effect of low serotonin in the brain. This experimental approach reduces...
Primary pellagra is due to a diet that does not contain enough niacin and tryptophan. Secondary pellagra is due to a poor ability to use the niacin within...
dinucleotide (NAD+). Metabolites involved in the kynurenine pathway include tryptophan, kynurenine, kynurenic acid, xanthurenic acid, quinolinic acid, and 3-hydroxykynurenine...
In enzymology, a tryptophan transaminase (EC 2.6.1.27) is an enzyme that catalyzes the chemical reaction L-tryptophan + 2-oxoglutarate ⇌ {\displaystyle...
Indoles are widely distributed in nature, most notably as amino acid tryptophan and neurotransmitter serotonin. Indole is a solid at room temperature...
manufactured tryptophan so that the bacteria would be more efficient. At the same time, they also changed the technique used to purify the tryptophan.: 327–328 ...
Tryptophan pyrrolase may refer to: Tryptophan 2,3-dioxygenase, an enzyme Indoleamine 2,3-dioxygenase, an enzyme This set index page lists enzyme articles...
In enzymology, a tryptophan dehydrogenase (EC 1.4.1.19) is an enzyme that catalyzes the chemical reaction L-tryptophan + NAD(P)+ + H2O ⇌ {\displaystyle...
Tryptophan hydroxylase 2 (TPH2) is an isozyme of tryptophan hydroxylase found in vertebrates. In humans, TPH2 is primarily expressed in the serotonergic...
hypercalcemia. It is caused by a defect in tryptophan absorption. Bacterial degradation of unabsorbed tryptophan in the intestine leads to excessive indole...
aromatic ring. Among the 20 standard amino acids, histidine, phenylalanine, tryptophan, tyrosine, are classified as aromatic. Aromatic amino acids, excepting...
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