Ornithine

Source: Wikipedia, the free encyclopedia.
l-Ornithine
Names
IUPAC name
L-Ornithine
Other names
(+)-(S)-2,5-Diaminovaleric acid
(+)-(S)-2,5-Diaminopentanoic acid
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
 100.000.665 Edit this at Wikidata
EC Number
  • 200-731-7
IUPHAR/BPS
KEGG
MeSH Ornithine
UNII
  • InChI=1S/C5H12N2O2/c6-3-1-2-4(7)5(8)9/h4H,1-3,6-7H2,(H,8,9)/t4-/m0/s1 checkY
    Key: AHLPHDHHMVZTML-BYPYZUCNSA-N checkY
  • 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
  • O=C(O)[C@@H](N)CCCN
Properties[1]
C5H12N2O2
Molar mass 132.16 g/mol
Melting point 140 °C (284 °F; 413 K)
soluble
Solubility soluble in ethanol
Acidity (pKa) 1.94
+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 verify (what is checkY☒N ?)

Ornithine is a

non-proteinogenic α-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.[2]

Role in urea cycle

L-Ornithine is one of the products of the action of the enzyme

guanidinium
compound) is hydrolysed back to ornithine, producing urea. The amino groups of urea come from the ammonia and aspartate, and the nitrogen in ornithine remains intact.

Reaction mechanism:. The side-chain amino group of ornithine (Orn) attacks the carbonyl carbon of carbamoyl phosphate (CP) nucleophilically, left, to form a tetrahedral transition state, middle. Charge rearrangement releases citrulline (Cit) and phosphate (Pi), right.[3]

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.[4]

Other reactions

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.

In bacteria, such as E. coli, ornithine can be synthesized from L-glutamate.[5]

Ornithine lactamization

Research

Exercise fatigue

L-Ornithine supplementation attenuated fatigue in subjects in a placebo-controlled study using a cycle ergometer. The results suggested that L-ornithine has an antifatigue effect in increasing the efficiency of energy consumption and promoting the excretion of ammonia.[6][7]

Weightlifting supplement

human growth hormone (HGH), muscle mass, and strength. A 1993 short 4-day clinical study reported that L-ornithine in combination with L-arginine and L-lysine at 2 g/d each did not increase HGH.[8] A review from 2002 on the topic concluded "The use of specific amino acids to stimulate GH release by athletes is not recommended."[9]

Cirrhosis

L-Ornithine L-aspartate (LOLA), a stable salt of ornithine and aspartic acid, has been used in the treatment of cirrhosis[10] and hepatic encephalopathy.[11]

References

  1. ISBN 0-8493-0462-8
    .
  2. PMID 27978498
    .
  3. PMID 10747936
    .
  4. S2CID 27957755
    .
  5. ^ "Ornithine Biosynthesis". School of Biological and Chemical Sciences, Queen Mary, University of London. Archived from the original on 2012-04-14. Retrieved 2007-08-17. {{cite journal}}: Cite journal requires |journal= (help)
  6. PMID 19083482
    .
  7. PMID 20717126
    .
  8. PMID 8220394
    .
  9. PMID 12093449
    .
  10. PMID 20642112
    .
  11. PMID 30706425
    .

External links

Wikimedia Commons has media related to L-Ornithine.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Ornithine&oldid=1194559796"