Triptófano: Diferenzas entre revisións

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Liña 59:
É un aminoácido esencial, é dicir, o noso metabolismo non o pode sintetizar e debemos tomalo na dieta. Está codificado por un só [[codón]] do [[código xenético]], o UGG (só hai outro aminoácido, a [[metionina]], codificado por un só codón).<ref name="dayhoff">{{cite web|title=Dr. Margaret Oakley Dayhoff|url=http://www.biology.arizona.edu/biochemistry/problem_sets/aa/Dayhoff.html|work=The Chemistry of Amino Acids|publisher=[[University of Arizona]]|accessdate=7 September 2010}}</ref> O [[estereoisómero]] do triptófano que aparece en practicamente todas as proteínas é o L-triptófano, pero o D-triptófano pódese atopar en certos péptidos naturais, como os do veleno ''contryphan'' do [[gasterópodo]] mariño ''Conus''.<ref name="Pallaghy_1999">{{Cita publicación periódica |author=Pallaghy PK, Melnikova AP, Jimenez EC, Olivera BM, Norton RS|title=Solution structure of contryphan-R, a naturally-occurring disulfide-bridged octapeptide containing D-tryptophan: comparison with protein loops|journal= Biochemistry |volume= 38 |issue= 35 |pages= 11553–9 |year= 1999 |pmid= 10471307 | doi = 10.1021/bi990685j}}</ref>
 
Foi illado por primeira vez por [[Frederick Hopkins]] en 1901<ref name="pmid16992614">{{Cita publicación periódica | author = Hopkienns FG, Cole SW | title = A contribution to the chemistry of proteids: Part I. A preliminary study of a hitherto undescribed product of tryptic digestion | journal = J. Physiol. (Lond.) | volume = 27 | issue = 4-5 | pages = 418–28 | year = 1901 | pmid = 16992614 | doi = | issn = | pmc = 1540554}}</ref> por [[hidrólise]] da [[caseína]]. De 600 g de caseína crúa poden obterse 4-8 g de triptófano <ref name="Cox_1943">{{Cita publicación| revista=OrgSyn | autor = Cox GJ, King H | título = L-Tryptophane | volume = 2 | páxinas = 612–616 | ano = 1943 | prep id= CV2P0612}}</ref>.
 
== Biosíntese e síntese industrial ==
Liña 87:
Hai probas de que é improbable que se alteren os niveis sanguíneos de triptófano por un cambio de dieta,<ref name="DOI10.1111/j.1601-5215.2010.00508.x">{{Cita publicación periódica | author = Soh, Nerissa L. AU - Walter, Garry TI | title = Tryptophan and depression: can diet alone be the answer? | journal = Acta Neuropsychiatrica VL | volume = 23 | issue = 1 | pages = 1601–5215; | year = 2011 | url = http://onlinelibrary.wiley.com/doi/10.1111/j.1601-5215.2010.00508.x/full | doi = 10.1111/j.1601-5215.2010.00508.x | issn =}}</ref> pero por algún tempo estivo vendéndose triptófano como suplemento alimentario nas tendas dietéticas. Moita xente atopaba que o triptófano axudaba a durmir, quizais porque aumentaba os niveis de serotonina (un neurotransmisor que a niveis moderados funciona como calmante)<ref name="pmid6115400">{{Cita publicación periódica | author = Wurtman RJ, Hefti F, Melamed E | title = Precursor control of neurotransmitter synthesis | journal = Pharmacol. Rev. | volume = 32 | issue = 4 | pages = 315–35 | year = 1980 | pmid = 6115400 | doi = | issn = | url = http://wurtmanlab.mit.edu/publications/pdf/466.pdf}}</ref> e [[melatonina]] ([[hormona]] que induce o sono).<ref name="pmid5300432">{{Cita publicación periódica | author = Wurtman RJ, Larin F, Axelrod J, Shein HM, Rosasco K | title = Formation of melatonin and 5-hydroxyindole acetic acid from 14C-tryptophan by rat pineal glands in organ culture | journal = Nature | volume = 217 | issue = 5132 | pages = 953–4 | year = 1968 | pmid = 5300432 | doi = 10.1038/217953a0}}</ref><ref name="pmid16942634">{{Cita publicación periódica | author = Ruddick JP, Evans AK, Nutt DJ, Lightman SL, Rook GA, Lowry CA | title = Tryptophan metabolism in the central nervous system: medical implications | journal = Expert reviews in molecular medicine | volume = 8 | issue = 20 | pages = 1–27 | year = 2006 | pmid = 16942634 | doi = 10.1017/S1462399406000068}}</ref>
 
Os resultados das probas clínicas realizadas obtiveron resultados contraditorios en canto á efectividade do triptófano como sedativo, especialmente en individuos normais.<ref name="pmid6764927">{{Cita publicación periódica | author = Hartmann E | title = Effects of L-tryptophan on sleepiness and on sleep | journal = Journal of psychiatric research | volume = 17 | issue = 2 | pages = 107–13 | year = 1982 | pmid = 6764927 | doi = 10.1016/0022-3956(82)90012-7}}</ref><ref name="pmid3090582">{{Cita publicación periódica | author = Schneider-Helmert D, Spinweber CL | title = Evaluation of L-tryptophan for treatment of insomnia: a review | journal = Psychopharmacology (Berl.) | volume = 89 | issue = 1 | pages = 1–7 | year = 1986 | pmid = 3090582 | doi = 10.1007/BF00175180}}</ref><ref name="pmid4097755">{{Cita publicación periódica | author = Wyatt RJ, Engelman K, Kupfer DJ, Fram DH, Sjoerdsma A, Snyder F. | title = Effects of L-tryptophan (a natural sedative) on human sleep | journal = Lancet | volume = 1970 Oct 24,2 | issue = 7678 | pages = 842–6 | year = 1970 Oct 24| pmid = 4097755 | doi = | issn = 0140-6736}}</ref> Ademais, o triptófano mostrou certa efectividade no tratamento doutras condicións tipicamente asociadas con niveis cerebrais de serotonina baixos<ref>{{cite web|title=research summary of Dr. Richard Wurtman, MIT|url=http://web.mit.edu/bcs/people/wurtman.shtml|accessdate = 2007-08-12}}</ref> como desordes premenstruais<ref name="pmid10023508">{{Cita publicación periódica | author = Steinberg S, Annable L, Young SN, Liyanage N | title = A placebo-controlled clinical trial of L-tryptophan in premenstrual dysphoria | journal = Biol. Psychiatry | volume = 45 | issue = 3 | pages = 313–20 | year = 1999 | pmid = 10023508 | doi = 10.1016/S0006-3223(98)00005-5}}</ref> e depresións estacionais.<ref name="pmid9114947">{{Cita publicación periódica | author = Lam RW, Levitan RD, Tam EM, Yatham LN, Lamoureux S, Zis AP | title = L-tryptophan augmentation of light therapy in patients with seasonal affective disorder | journal = Canadian Journal of Psychiatry | volume = 42 | issue = 3 | pages = 303–6 | year = 1997 | pmid = 9114947 | doi = | issn = | url = http://ww1.cpa-apc.org:8080/Publications/Archives/CJP/1997/April/apr97_bc1.htm}}</ref><ref name="Jepson_1999">{{Cita publicación periódica |author=Jepson TL, Ernst ME, Kelly MW|title=Current perspectives on the management of seasonal affective disorder|journal= J Am Pharm Assoc (Wash) |volume= 39 |issue= 6 |pages= 822–9 |year= 1999 |pmid= 10609448}}</ref> En particular, o triptófano mostrou ser moi prometedor como [[antidepresivo]] administrado só<ref name="pmid7156248">{{Cita publicación periódica | author = Thomson J, Rankin H, Ashcroft GW, Yates CM, McQueen JK, Cummings SW | title = The treatment of depression in general practice: a comparison of L-tryptophan, amitriptyline, and a combination of L-tryptophan and amitriptyline with placebo | journal = Psychological medicine | volume = 12 | issue = 4 | pages = 741–51 | year = 1982 | pmid = 7156248 | doi = 10.1017/S0033291700049047| issn =}}</ref> ou xunto con fármacos antidepresivos.<ref name="pmid7156248" /><ref name="pmid11022398">{{Cita publicación periódica | author = Levitan RD, Shen JH, Jindal R, Driver HS, Kennedy SH, Shapiro CM | title = Preliminary randomized double-blind [[placebo]]-controlled trial of tryptophan combined with fluoxetine to treat major depressive disorder: antidepressant and hypnotic effects | journal = Journal of psychiatry & neuroscience : JPN | volume = 25 | issue = 4 | pages = 337–46 | year = 2000 | pmid = 11022398 | doi = | issn = | url = http://www.cma.ca/index.cfm/ci_id/12652/la_id/1.htm | pmc = 1407729}}</ref> Porén, a fiabilidade destas probas clínicas foi cuestionada.<ref name="pmid10696120">{{Cita publicación periódica | author = Meyers S | title = Use of neurotransmitter precursors for treatment of depression | journal = Alternative medicine review : a journal of clinical therapeutic | volume = 5 | issue = 1 | pages = 64–71 | year = 2000 | pmid = 10696120 | doi = | issn = | url = http://www.thorne.com/altmedrev/.fulltext/5/1/64.pdf}}</ref><ref name="pmid11869656">{{Cita publicación periódica | author = Shaw K, Turner J, Del Mar C | editor1-last = Shaw | editor1-first = Kelly A | title = Tryptophan and 5-hydroxytryptophan for depression | journal = Cochrane database of systematic reviews (Online) | volume = | issue = 1 | pages = CD003198 | year = 2002 | pmid = 11869656 | doi = 10.1002/14651858.CD003198}}</ref>
 
== Fármacos derivados do triptófano ==