Tryptophan

tryptophan

[′trip·tə‚fan]

(biochemistry)

C₁₁H₁₂O₂N₂ An amino acid obtained from casein, fibrin, and certain other proteins; it is a precursor of indoleacetic acid, serotonin, and nicotinic acid.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Tryptophan

 

β-(β-indolyl)-α-aminopropionic acid, one of the most important natural amino acids. It exists in the form of optically active L- and D- forms and a racemic DL-form. L-tryptophan is a minor constituent of gamma globulins, fibrinogen, casein, and other proteins.

L-tryptophan is an essential amino acid. The daily requirements for adults and children up to seven years of age are 0.25 g and about 1 g, respectively. Tryptophan is synthesized in microorganisms and plants by condensation of the amino acid serine with indole, which is catalyzed by the enzyme tryptophan synthetase. (The biosynthesis of tryptophan in E. coli was used to demonstrate the collinearity of a gene and the polypeptide chain coded by that gene, in which the position of each amino acid in the polypeptide chain is determined by a special portion of the gene.) L-tryptophan undergoes complex transformations in animals, forming a number of essential compounds: its decomposition products are the basis for the formation of nicotinic acid and serotonin in humans and other mammals, eye pigments (ommo-chromes) in insects, and heteroauxins, indigo, and several alkaloids in plants. Skatole and indole are formed from tryptophan during putrefactive processes in the intestine. During the normal breakdown in the body, six of the 11 carbon atoms of tryptophan are included in the Krebs cycle through acetyl and acetoacetyl coenzyme A, and the other five are converted to CO₂.

In humans, the congenital absence of tryptophan pyrrolase, the enzyme that oxidizes tryptophan, results in feeblemindedness. Disruption of tryptophan metabolism in humans may be indicative of several serious diseases, including tuberculosis, cancer, and diabetes. Functional and organic disorders may also be caused by an insufficiency of tryptophan in the human diet and animal feed, resulting from the low content of tryptophan in many natural proteins. The food value of many proteins can be increased through the addition of synthetic tryptophan, obtained by chemical synthesis from acrylonitrile, ammonia, hydrogen cyanide, or phenylhydrazine. Techniques for enzymic synthesis of tryptophan from indole, pyruvic acid, and ammonia are under development.

REFERENCES

Braunshtein, A. E. Biokhimiia aminokislotnogo obmena. Moscow, 1949.
Lehninger, A. Biokhimiia. Moscow, 1974. (Translated from English.)
Meister, A. Biokhimiia aminokislot. Moscow, 1961. (Translated from English.)
Safonova, E. N., and V. M. Belikov. “Uspekhi v oblasti sinteza i proizvodstva a-aminokislot.” Uspekhi khimii, 1974, vol. 43, no. 9.

E. N. SAFONOVA

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.