Ornithine

L-Ornithine

Names
IUPAC name L-Ornithine
Other names (+)-(S)-2,5-Diaminovaleric acid, (+)-(S)-2,5-Diaminopentanoic acid
Identifiers
CAS Number	70-26-8 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:15729 N
ChemSpider	6026 Y
DrugBank	DB00129 N
ECHA InfoCard	100.000.665
EC Number	200-731-7
IUPHAR/BPS	725
KEGG	D08302 Y
MeSH	Ornithine
PubChem CID	389
UNII	E524N2IXA3 Y
InChI InChI=1S/C5H12N2O2/c6-3-1-2-4(7)5(8)9/h4H,1-3,6-7H2,(H,8,9)/t4-/m0/s1 Y Key: AHLPHDHHMVZTML-BYPYZUCNSA-N Y InChI=1/C5H12N2O2/c6-3-1-2-4(7)5(8)9/h4H,1-3,6-7H2,(H,8,9)/t4-/m0/s1 InChI=1/C5H12N2O2/c6-3-1-2-4(7)5(8)9/h4H,1-3,6-7H2,(H,8,9)/t4-/m0/s1 Key: AHLPHDHHMVZTML-BYPYZUCNBZ
SMILES O=C(O)[C@@H](N)CCCN
Properties
Chemical formula	C5H12N2O2
Molar mass	132.16 g/mol
Melting point	140 °C (284 °F; 413 K)
Solubility in water	soluble
Solubility	soluble in ethanol
Acidity (pKa)	1.94
Chiral rotation ([α]D)	+11.5 (H2O, c = 6.5)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Ornithine is a non proteinogenic amino acid that plays a role in the urea cycle. Ornithine is abnormally accumulated in the body in ornithine transcarbamylase deficiency. The radical is ornithyl.

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 (H
2NC(O)OPO2−
3). Ornithine is converted into a urea derivative at the δ (terminal) nitrogen by carbamoyl phosphate synthetase. 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 is not an amino acid coded for by DNA, that is, not proteinogenic. 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.

Ornithine, via the action of ornithine decarboxylase (E.C. 4.1.1.17), is the starting point for the synthesis of polyamines such as putrescine.