ornithine
2,5-Diaminovaleric acid; the l-isomer is the amino acid formed when l-arginine is hydrolyzed by arginase; not a constituent of proteins, but an important intermediate in the urea cycle; elevated levels seen in certain defects of the urea cycle.
- o. δ-aminotransferase an enzyme that will reversibly catalyze the reaction of α-ketoglutarate and l-o. to form l-glutamate and l-glutamate γ-semialdehyde; a deficiency of this enzyme will result in gyrate atrophy of the choroid and retina. SYN: o. transaminase.
- o. carbamoyltransferase an enzyme catalyzing formation of l-citrulline and orthophosphate from l-o. and carbamoyl phosphate; a part of the urea cycle; a deficiency of this enzyme will result in ammonia intoxication and impaired urea formation. SYN: o. transcarbamoylase.
- o. decarboxylase an enzyme catalyzing the decarboxylation of l-o. to putrescine and CO2; first step in polyamine biosynthesis.
- o. transaminase SYN: o. δ-aminotransferase.
- o. transcarbamoylase SYN: o. carbamoyltransferase.

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or·ni·thine 'ȯr-nə-.thēn n a crystalline amino acid C5H12N2O2 that functions esp. in urea production as a carrier by undergoing conversion to citrulline and then arginine in reaction with ammonia and carbon dioxide followed by recovery along with urea by enzymatic hydrolysis of arginine

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n.
an amino acid produced in the liver as a by-product during the conversion of ammonia to urea.

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or·ni·thine (orґnĭ-thēn) an amino acid produced in the urea cycle by the splitting off of urea from arginine and is itself converted into citrulline. On decomposition, it gives rise to putrescine.

Medical dictionary. 2011.

Look at other dictionaries:

  • Ornithine — Formule topologique de l ornithine. Général No CAS …   Wikipédia en Français

  • ornithine — ornithine. См. орнитин. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • ornithine — ● ornithine nom féminin Acide aminé basique, glycoformateur et transaminable, jouant un rôle dans le cycle de l uréogenèse. (Le dérivé guanidinique est l arginine.) …   Encyclopédie Universelle

  • ornithine — [ôr′nə thēn΄, ôr′nəthin] n. [< Gr ornis, bird (see ORNITHO ) + INE3] a nonessential amino acid, NH2 (CH2) 3CH(NH2)COOH, found in animals as a product of urea formation from proteins and in the excrement of birds …   English World dictionary

  • Ornithine — L Ornithine IUPAC name L Ornithine …   Wikipedia

  • ornithine — noun Etymology: International Scientific Vocabulary ornithuric acid (a compound of which ornithine is a component, found in the urine of birds) + 2 ine Date: 1881 a crystalline amino acid C5H12N2O2 that functions especially in urea production as… …   New Collegiate Dictionary

  • ornithine — ornitinas statusas T sritis chemija formulė H₂N(CH₂)₃CH(NH₂)COOH santrumpa( os) Orn atitikmenys: angl. ornithine rus. орнитин ryšiai: sinonimas – 2,5 diaminopentano rūgštis …   Chemijos terminų aiškinamasis žodynas

  • ornithine — noun an amino acid that does not occur in proteins but is important in the formation of urea • Hypernyms: ↑amino acid, ↑aminoalkanoic acid * * * ornithine Chem. (ˈɔːnɪθaɪn) [f. Gr. ὀρνῑθ bird + ine5.] A base, C5H12N2O2, which enters into the… …   Useful english dictionary

  • ornithine — /awr neuh theen /, n. Biochem. an amino acid, H2N(CH2)3CH(NH2)COOH, obtained by the hydrolysis of arginine and occurring as an intermediate compound in the urea cycle of mammals. [1880 85; ornith(uric acid), secreted by birds + INE2] * * * …   Universalium

  • ornithine — noun An amino acid, 2,5 diaminopentanoic acid, that is not present in protein, but is an intermediate in the biosynthesis of urea …   Wiktionary

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