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An amino acid, C6H13N3O3, originally isolated from watermelon, that is produced as an intermediate in the conversion of ornithine to arginine during urea formation in the liver.

[New Latin Citrullus, watermelon genus (from Medieval Latin citrullus, watermelon, from Italian dialectal citrulo, from Late Latin citrium, from Latin citrus, citron) + -ine.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Biochemistry) an amino acid that occurs in watermelons and is an intermediate in the formation of urea. Formula: NH2CONH(CH2)3CHNH2COOH
[C20: from Medieval Latin citrullus a kind of watermelon, from Latin citron, referring to its colour]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈsɪ trəˌlin)

an amino acid, C6H13N3O3, abundant in watermelons and an intermediate compound in the urea cycle.
[1930; < New Latin Citrull(us) the watermelon genus (ultimately derivative of Latin citrus citrus)]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.citrulline - an amino acid that does not occur in proteins but is an intermediate in the conversion of ornithine to arginine
amino acid, aminoalkanoic acid - organic compounds containing an amino group and a carboxylic acid group; "proteins are composed of various proportions of about 20 common amino acids"
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References in periodicals archive ?
The diagnoses made were long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (confirmed by mutation analysis), carnitine transporter defect (confirmed by cultured fibroblast fatty acid oxidation), and citrullinemia (confirmed by cultured fibroblast citrulline incorporation).
Citrulline is an unusual amino acid resulting from an enzymatically posttranslationally modified arginine residue.
The CVs for most free amino acids of the four sample types (n = 172) were between 12% and 42%, except for the following amino acids: phosphoethanolamine (PTEN), aspartic acid (Asp), hydroxyproline (Hyp), citrulline (Cit), [beta]-alanine, ethanolamine, and Trp.
A favorite summer picnic fruit, watermelon has few calories and is a good source of two powerful plant compounds -- citrulline and lycopene.
Cinnamaldehyde is a dye that stains citrulline, which is abundant in the inner root sheath, and can be a tool in identifying its presence and/or aberrations.4 A trichogram of the pulled hairs in a patient with LAHS may classically show ruffled appearance of the cuticle, misshapen anagen hair bulbs, and absence of the inner root sheath.
That's because the popular summer fruit is richer than experts believed in an amino acid called citrulline, which relaxes and dilates blood vessels much like Viagra and other drugs meant to treat erectile dysfunction (ED).
7.Watermelon can help with blood pressure and heart health New research shows the citrulline and arginine supplements derived from watermelon extract lead to significant improvements in blood pressure and cardiac stress in obese study participants.
Investigations have indicated that some amino acids, including glutamine, arginine, ornithine, citrulline, tryptophan, valine, and leucine, could be efficient nitrogen source for dermatophytes.8-10 Some amino acids have also antifungal effects on dermatophytes.
Test results did not detect citrulline antibodies, and the single patient with positive rheuma factor had no arthritic symptoms.
Plasma amino acid examination (high-performance liquid chromatography) on 2 occasions revealed increased arginine at 309 and 377 (reference interval, 15-160) ^mol/L and ornithine at 210 and 361 (30-150) ^mol/L, while all other amino acids including citrulline and glutamine were within reference limits.