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a naturally occurring amino acid, one of the essential amino acids; it is a precursor of serotonin. Adequate levels in the diet may mitigate pellagra by compensating for deficiencies of niacin.

tryp·to·phan (Trp, W),

2-Amino-3-(3-indolyl)propionic acid; the l-isomer is a component of proteins; a nutritionally essential amino acid.


/tryp·to·phan/ (Trp) (W) (trip´to-fan) a naturally occurring amino acid, existing in proteins and essential for human metabolism. It is a precursor of serotonin. Adequate levels may mitigate pellagra by compensating for deficiencies of niacin.


(trĭp′tə-făn′) also


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.

tryptophan (Trp)

an amino acid essential for normal growth and nitrogen balance. Tryptophan is the precursor of several important biomolecules, including serotonin and niacin. See also amino acid, protein.
enlarge picture
Chemical structure of tryptophan


An essential amino acid, which is a key building block in protein biosynthesis. It is a precursor for serotonin (a neurotransmitter) and niacin (a B vitamin).

Dietary sources
Milk, sesame seeds, soy beans, spirulina, sunflower seeds, cashews.
Fringe nutrition
Tryptophan has been promoted for its alleged ability to induce sleep, and as an antidepressint.


(W) (trip'tŏ-fan)
A nutritionally essential amino acid; the l-isomer is a component of proteins.


An antidepressant drug. L-tryptophan, sold in USA as a non-prescription food additive was withdrawn by the American Food and Drugs Administration (FDA) because of reports of a severe muscle disorder apparently caused by an unidentified contaminant. It is used only by hospital specialists who are aware of the risks. A brand name is Optimax.
Tryptophanclick for a larger image
Fig. 306 Tryptophan . Molecular structure.

tryptophan (W, Trp)

one of 20 AMINO ACIDS common in protein. It has a nonpolar ‘R’ group structure and is relatively insoluble in water. See Fig. 306 . The ISOELECTRIC POINT of tryptophan is 5.9.


An essential amino acid that has to consumed in the diet because it cannot be manufactured by the body. Tryptophan is converted by the body to niacin, one of the B vitamins.
Mentioned in: Hartnup Disease

tryptophan (tripˑ·t·fan),

n an essential amino acid used in the treatment of insomnia, depression, behavioral disorders, stress, and premenstrual syndrome (PMS). Also called
Enlarge picture
Chemical structure of tryptophan.


(Trp, W) (trip'tŏ-fan)
A nutritionally essential amino acid.

tryptophan, tryptophane

Trp; a naturally occurring amino acid, existing in proteins. High levels of intake of d,l-tryptophan are thought to be a significant cause of atypical interstitial pneumonia in cattle. The actual toxic agent is 3-methylindole, a metabolic product of d,l-tryptophan in the rumen.

D, L-tryptophan
component of some roughages; high levels can cause acute bovine pulmonary emphysema and edema.
tryptophan oxygenase
first enzyme in the catabolic pathway for tryptophan. Essential step in the pathway to synthesis of nicotinamide nucleotides NAD+ and NADP+. Approximately 30% of the nicotinamide nucleotide requirement of some animals can be supplied through this enzyme. The cat is notably lacking in the latter capacity.