| Share
 

tryptophan

tryptophan (trĭpˈtəfăn) [key], organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l -stereoisomer appears in mammalian protein. It is one of several essential amino acids needed in the diet; human beings cannot synthesize it from simpler metabolites. Young adults require about 7 mg of this amino acid per day per kg (3 mg per lb) of body weight. Nicotinic acid (niacin), a vitamin of the B complex, can be made from tryptophan in the body, but evidently the rate of transformation is insufficient for the demands of normal growth and maintenance, and hence nicotinic acid must be supplied in the diet. Deficiency of tryptophan in the diet enhances the progress of the vitamin-deficiency disease pellagra, which is treated by restoring nicotinic acid to the diet, usually supplemented with tryptophan. Bacteria in the intestine break tryptophan down to compounds such as skatole and indole, which to a great extent are responsible for the unpleasant odor of feces. Tryptophan contributes to the structure of proteins into which it has been incorporated by the tendency of its side chain to participate in hydrophobic interactions (see isoleucine). The amino acid was isolated from casein (milk protein) in 1901, and its structure was established in 1907.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on tryptophan from Infoplease:

See more Encyclopedia articles on: Biochemistry


Premium Partner Content
HighBeam Research
Documents Images and Maps Reference
(from Newspapers, Magazines, Journals, Newswires, Transcripts and Books)

Research our extensive archive of more than 80 million articles from 6,500 publications.

Additional search results provided by HighBeam Research, LLC. © Copyright 2005. All rights reserved.

24 X 7

Private Tutor

Click Here for Details
24 x 7 Tutor Availability
Unlimited Online Tutoring
1-on-1 Tutoring