Ornithine
Structural formula | ||||||||||||||||||||||
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General | ||||||||||||||||||||||
Surname | L - (+) - ornithine | |||||||||||||||||||||
other names |
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Molecular formula | C 5 H 12 N 2 O 2 | |||||||||||||||||||||
Brief description |
colorless crystals |
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properties | ||||||||||||||||||||||
Molar mass | 132.2 g mol −1 | |||||||||||||||||||||
Physical state |
firmly |
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Melting point |
140 ° C |
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solubility |
Easily soluble in water with an alkaline reaction |
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safety instructions | ||||||||||||||||||||||
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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
- ↑ a b c d Entry on l-ornithine. In: Römpp Online . Georg Thieme Verlag, accessed on June 20, 2014.
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ↑ 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 .
- ↑ Entry on Bacitracin. In: Römpp Online . Georg Thieme Verlag, accessed on June 20, 2014.