from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. An essential amino acid, C11H12N2O2, formed from proteins during digestion by the action of proteolytic enzymes. It is necessary for normal growth and development and is the precursor of several substances, including serotonin and niacin.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. An essential amino acid having an indole side chain; it is present in many foods, especially chocolate, oats, bananas and milk; it is essential for normal growth and development and is the precursor of serotonin and niacin; any specific form of this compound, or any derivative of it.

from The Century Dictionary and Cyclopedia

  • n. Same as proteinochromogen.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. an amino acid that occurs in proteins; is essential for growth and normal metabolism; a precursor of niacin


from The American Heritage® Dictionary of the English Language, 4th Edition

tryptic, of trypsin (formed on the model of pepsin, peptic); see trypsin + -phan(e).

from Wiktionary, Creative Commons Attribution/Share-Alike License

From German Tryptophan, corresponding to tryptic + Ancient Greek ϕαίνειν ("to appear").


  • In plants, the tryptophan is produced endogenously where in animals the tryptophan used comes from diet.

    Enterprising chemistry majors at Georgetown

  • This is because bananas contain tryptophan, a type of protein that the body converts into serotonin, known to make you relax, improve your mood and generally make you feel happier.

    20 Fascinating Facts About the Natural Healing Power of Bananas

  • To make matters more interesting, tryptophan is present in many protein-rich foods, which have been found to prevent serotonin production.

    Lactose Makes You Sleepy?

  • This Cambridge biochemist was already well known for having isolated the amino acid tryptophan from a protein and demonstrated its essential nature.

    The Nobel Prize and the Discovery of Vitamins

  • It might be pointed out here that kynurenine has since been recognized to occupy a central position in tryptophan metabolism in many organisms aside from insects, including mammals and fungi.

    Edward Tatum - Nobel Lecture

  • -0/+2its surprising to hear the word tryptophan without an ignorant remark about how sleepy it makes you. dugg for that alone. just now, -0/+0Slightly inaccurate about turkeys flying.

    Original Signal - Transmitting Digg

  • It is similar to tryptophan, which is the amino acid that gets converted into serotonin—5-HTP is the intermediate step in that process.

    The Chemistry of Calm

  • Here's a brief explanation of the mechanism behind the effect of food on serotonin levels: after consumption of a carbohydrate-rich meal, the hormone insulin is secreted, which causes a lowering of the blood levels of most amino acids (the building blocks of protein), with the exception of tryptophan, which is a precursor to serotonin.

    Lactose Makes You Sleepy?

  • -- Ronald Duffy, Santa Fe, N. M.There is no nutritional difference between warm and cold cow's milk -- and both contain the amino acid tryptophan, which is known to have sedative effects.

    Ask Tip Sheet

  • Turkey contains an amino acid called tryptophan that can make you feel a little tired.

    CNN Transcript Nov 27, 2004


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