CAS number 70-26-8 YesY
PubChem 6262
ChemSpider 6026 YesY
EC-number 200-731-7
DrugBank DB00129
KEGG D08302 YesY
MeSH Ornithine
Jmol-3D images Image 1
Molecular formula C5H12N2O2
Molar mass 132.16 g/mol
Melting point

140 ºC

Solubility in water soluble
Chiral rotation [α]D +11.5 (H2O, c = 6.5)
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ornithine is an amino acid that plays a role in the urea cycle.

Role in urea cycle

L-Ornithine is one of the products of the action of the enzyme arginase on L-arginine, creating urea. Therefore, ornithine is a central part of the urea cycle, which allows for the disposal of excess nitrogen. Ornithine is recycled and, in a manner, is a catalyst. First, ammonia is converted into carbamoyl phosphate (phosphate-CONH2), which creates one half of urea. Ornithine is converted into a urea derivative at the δ (terminal) nitrogen by carbamoyl phosphate. Another nitrogen is added from aspartate, producing the denitrogenated fumarate, and the resulting arginine (a guanidinium compound) is hydrolysed back to ornithine, producing urea. The nitrogens of urea come from the ammonia and aspartate, and the nitrogen in ornithine remains intact.

Ornithine lactamization

Ornithine is not an amino acid coded for by DNA, and, in that sense, is not involved in protein synthesis. However, in mammalian non-hepatic tissues, the main use of the urea cycle is in arginine biosynthesis, so, as an intermediate in metabolic processes, ornithine is quite important. It is believed not to be a part of genetic code because polypeptides containing unprotected ornithines undergo spontaneous lactamization.[2]

Other reactions

Ornithine, via the action of ornithine decarboxylase (E.C., is the starting point for the synthesis of polyamines such as putrescine.

In bacteria, such as E. coli, ornithine can be synthesized from L-glutamate.[3]

Ornithine is also the starting point for cocaine biosynthesis, when decarboxylased, then modified greatly by Cytochrome P450.


  1. ^ Weast, Robert C., ed (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. p. C-408. ISBN 0-8493-0462-8. .
  2. ^ Arthur L. Weber and Stanley L. Miller (1981). "Reasons for the Occurrence of the Twenty Coded Protein Amino Acids". J. Mol. Evol. 17 (5): 273–284. doi:10.1007/BF01795749. PMID 7277510. http://physwww.mcmaster.ca/~higgsp/3D03/WeberReasons.pdf. 
  3. ^ Ornithine Biosynthesis. School of Biological and Chemical Sciences, Queen Mary, University of London. http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/AminoAcid/Orn.html. Retrieved 2007-08-17 .

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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 — 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 transcarbamylase — Ornithine carbamoyltransferase Human OTC trimer. From PDB 1OTH …   Wikipedia

  • Ornithine decarboxylase — Identifiers EC number CAS number 9024 60 6 …   Wikipedia

  • Ornithine translocase deficiency — Classification and external resources Ornithine ICD 9 …   Wikipedia

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