Ornithine


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ornithine

[′ȯr·nə‚thēn]
(biochemistry)
C5H12O2N2 An amino acid occurring in the urine of some birds, but not found in native proteins.

Ornithine

 

H2N(CH2)3CH(NH2)COOH (also α, δ-di-aminovaleric acid), an amino acid that is readily soluble in water and alcohol.

Ornithine has one asymmetric carbon atom and exists in two optically active forms (D- and L-) and one racemic form, L-ornithine, found in the tissues of animals and humans, plays an important role in the biosynthesis of urea by the ornithine cycle. It is formed from arginine and α-amino-y-formylbutyric acid and may be converted to proline. Free L-ornithine is found in plants; bound L-ornithine is a component of several peptide antibiotics (bacitracin and gramicidin). L-ornithine has not been isolated from natural proteins.

References in periodicals archive ?
Increased tissue arginase enzyme activity and ornithine levels together appear to enlarge in polyamine formation, which would lead to cancer development.
2] partial pressure; IEM, inborn error of metabolism; OTC, ornithine transcarbamylase; CVVH, continuous venovenous hemofiltration.
Plasma amino acid analysis revealed absence of citrulline and argininosuccinic acid, low normal ornithine, and high urinary orotic acid levels consistent with proximal urea cycle defects like Ornithine Transcarbamylase deficiency (OTC), N-acetyl Glutamate Synthase deficiency (NAGS), and Carbomyl Phosphate Synthase 1 deficiency (CPS1).
In-creased frequency of spontaneous skin tumors in transgenic mice which over-express ornithine decarboxylase.
Four of the seven identified metabolites--histidine, arginine, ornithine and glutamine--are related to genes involved in arginine-glutamine metabolism and nitrogen compound biosynthesis.
Tamir and Ratner (1963) attributed birds' incapacity to synthesize ornithine, citrulline and Arg to the absence of another enzyme key to the urea cycle, ornithine carbamoyltransferase (Figure 2).
Measurement of OAT activity: The activity of ornithine aminotransferase (OAT) was determined as described by Wu et al.
It is important to mention that because the Lowry method to determine the protein concentration does not measure fibrous proteins like collagen and elastin, proteins synthesized during the tissue healing process, and it is known that diabetes causes damage to the microvasculature [41, 42] and that ornithine, a product derived from arginine hydrolysis, can be used to synthetize proline, an amino acid needed for collagen synthesis, we decided to express the concentration of biomolecules related to dry weight.
Compelling evidence demonstrates that the combination of arginine and ornithine augments the results of resistance training by helping to increase lean body mass and strength.
professor of medicine and biological chemistry at the University of California, Irvine, presented "late-breaking" results from a phase III trial of difluoromethylornithine (DFMO), a synthetic inhibitor of ornithine decarboxylase, and sulindac (Clinoril), a nonsteroidal, anti-inflammatory drug (NSAID), in 375 patients.
The enzymatic activity of ornithine decarboxylase (ODC), which is one of the limiting enzymes of PAs biosynthesis, is not well regulated in can cer cells, participating in the transformation of cell phenotype from normal to malignant (Babbar and Gerner, 2003).