L-Tryptophan

L-Tryptophan is an essential amino acid that is used in the biosynthesis of proteins. It contains an amino group, a carboxyl group, and a side chain indole, making it a non-polar, aromatic amino acid. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet. L-Tryptophan is also a precursor to the neurotransmitter serotonin, the hormone melatonin, and vitamin B3.

Structure and Properties

L-Tryptophan is a white to yellowish-white crystalline powder that is slightly soluble in water. It is one of the 20 standard amino acids, as well as one of the few amino acids that have a chiral side chain. L-Tryptophan is classified as an essential amino acid because our bodies can’t make it, so diet must supply tryptophan.

Biosynthesis and Industrial Production

In bacteria that synthesize tryptophan, high cellular levels of this amino acid activate a repressor protein, which binds to the trp operon. Binding of this repressor to the tryptophan operon prevents transcription of downstream DNA that codes for the enzymes involved in the biosynthesis of tryptophan. So high levels of tryptophan prevent additional tryptophan synthesis through a negative feedback loop. Even though animals and humans cannot synthesize tryptophan, they need it for important biological functions and must obtain it from their diet.

Dietary Sources

L-Tryptophan is found in most protein-based foods or dietary proteins. It is particularly plentiful in chocolate, oats, dried dates, milk, yogurt, cottage cheese, red meat, eggs, fish, poultry, sesame, chickpeas, almonds, sunflower seeds, pumpkin seeds, buckwheat, spirulina, and peanuts.

Health Benefits and Uses

L-Tryptophan is used for insomnia, sleep apnea, depression, anxiety, facial pain, a severe form of premenstrual syndrome called premenstrual dysphoric disorder (PMDD), smoking cessation, grinding teeth during sleep (bruxism), attention deficit-hyperactivity disorder (ADHD), Tourette's syndrome, and to improve athletic performance.

Safety and Side Effects

L-Tryptophan is generally well tolerated by most people when used under the supervision of a healthcare provider. It can cause some side effects such as heartburn, stomach pain, belching and gas, nausea, vomiting, diarrhea, and loss of appetite. It can also cause headache, lightheadedness, drowsiness, dry mouth, visual blurring, muscle weakness, and sexual problems.

See Also

• Amino acid
• Serotonin
• Melatonin
• B3