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L-Ornithine L-Ornithine
Healthy Protein Metabolism

"DID You Know"
Plays a central role in the urea cycle, functioning along with Arginine and Citrulline to rid the body of ammonia, a byproduct of protein metabolism.!


What is L-Ornithine?

L-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.

Where does L-Ornithine come from?

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 (H2NC(O)OPO2-3). Ornithine is converted into a urea derivative at the d (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.

Who needs it and what are some symptoms of deficiency?

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.

How much should be taken? Are there side effects?

Always follow manufactures instruction and those of your physician when taking any supplements.

Recent Studies

  • Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. p. C-408. ISBN 0-8493-0462-8.
  • Weber AL, Miller SL (1981). "Reasons for the occurrence of the twenty coded protein amino acids" (PDF). Journal of Molecular Evolution. 17 (5): 273–84. Bibcode:1981JMolE..17..273W. doi:10.1007/BF01795749. PMID 7277510. S2CID 27957755.
  • "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.
  • Sugino T, Shirai T, Kajimoto Y, Kajimoto O (November 2008). "L-ornithine supplementation attenuates physical fatigue in healthy volunteers by modulating lipid and amino acid metabolism". Nutrition Research. 28 (11): 738–43. doi:10.1016/j.nutres.2008.08.008.
Realted Pages:

Amino Acids Branch Chain Amino Acids