tryptophan

American  

[trip-tuh-fan] / ˈtrɪp təˌfæn /

Also tryptophane

noun

Biochemistry.

1. an essential amino acid, (C 8 H 6 N)CH 2 CH(NH2 )COOH, colorless, crystalline, and aromatic, released from proteins by tryptic digestion and a precursor of serotonin. Trp; W

---

tryptophan British  

/ ˈtrɪptəˌfæn /

noun

1. an essential amino acid; a component of proteins necessary for growth

---

tryptophan Scientific  

/ trĭp′tə-făn′ /

1. An essential amino acid. Chemical formula: C ₁₁ H ₁₂ N ₂ O ₂ .

2. See more at amino acid

---

Etymology

Origin of tryptophan

1900–05; trypto- (irregular combining form representing Greek trīptós “rubbed”) + -phan(e) ( def. )

Example Sentences

As a result, tryptophan is redirected toward the kynurenic pathway, which produces neurotoxic compounds, while the production of protective neurotransmitters such as serotonin and melatonin declines.

From Science Daily • Jan. 15, 2026

Until now, however, researchers did not know what caused the brain to shift how it uses tryptophan in the first place.

From Science Daily • Jan. 15, 2026

The nutrients are involved in converting tryptophan into the sleep-promoting hormone melatonin, she said.

From The Wall Street Journal • Dec. 29, 2025

Partly because I was exhausted from the tryptophan I had ingested with my turkey the day before and could not get out of bed.

From The Wall Street Journal • Nov. 28, 2025

Beans have both lysine and tryptophan, but not the amino acids cysteine and methionine, which are provided by maize.

From "1491" by Charles C. Mann