Ornithine

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Structural formula
Structural formula of L-ornithine
General
Surname L - (+) - ornithine
other names
  • ( S ) - (+) - ornithine
  • ( S ) - (+) - 2,5-diaminopentanoic acid
  • L - (+) - diaminovaleric acid
  • Abbreviation: Orn
Molecular formula C 5 H 12 N 2 O 2
Brief description

colorless crystals

External identifiers / databases
CAS number 70-26-8
EC number 200-731-7
ECHA InfoCard 100,000,665
PubChem 6262
ChemSpider 6026
DrugBank DB00129
Wikidata Q410198
Drug information
ATC code

A05 BA50

properties
Molar mass 132.2 g mol −1
Physical state

firmly

Melting point

140 ° C

solubility

Easily soluble in water with an alkaline reaction

safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Ornithine (from Greek ornis , bird) is a basic, non-proteinogenic α- amino acid . In the L form it occurs mainly in the urea cycle as a carrier substance.

Manufacturing

L -Ornithine was first produced by Jaffé in 1877 from chicken excrement. The technical production of L- ornithine takes place by hydrolysis of L - arginine in an alkaline medium.

Role in the urea cycle

L -Ornithine is formed in the urea cycle with catalysis of arginase from L - arginine through the incorporation of water and the release of urea (NH 2 –CO – NH 2 ).

L- ornithine then combines, catalyzed by ornithine-carbamoyl phosphate transferase, with carbamoyl phosphate , splitting off its phosphate, and thus forms L - citrulline .

The argininosuccinate synthetase then catalyzes the condensation with L - aspartic acid while consuming ATP . The result is arginine succinic acid , which under physiological conditions is present as argininosuccinate, the anion.

L- argininosuccinate is split into fumarate and L -arginine by L -argininosuccinate lyase . L- arginine can now release urea again. L -Ornithine is thus available again and the reaction cycle closes.

Applications

Ornithine also plays a role in the MIO test in microbiology . Research shows that athletic performance in combination with ornithine and arginine can influence the formation of growth hormones . A reaction with ornithine can be recognized by the color of the agar in the tube:

  • Positive reaction: the tube remains colored purple
  • Negative reaction: tube shows yellow color

Isomerism

L -Ornithine is ( S ) -configured at the stereogenic center (α-carbon atom) . Enantiomer to L -ornithine- is in bacitracin occurring D -ornithine-. This is ( R ) -configured and only of minor importance.

Individual evidence

  1. ↑ a b c d Entry on l-ornithine. In: Römpp Online . Georg Thieme Verlag, accessed on June 20, 2014.
  2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  3. ↑ A. Zajac, S. Poprzecki, A. Zebrowska, M. Chalimoniuk, J. Langfort: Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes. In: J Strength Cond Res. 24 (4), 2010, pp. 1082-1090. PMID 20300016 .
  4. ↑ Entry on Bacitracin. In: Römpp Online . Georg Thieme Verlag, accessed on June 20, 2014.

Web links

Wikibooks: Urea Cycle  - Learning and Teaching Materials