Ornithine
Non-protein amino acid central to the urea cycle. Supports ammonia detoxification and may enhance sleep.
Ornithine is a non-protein amino acid (not used to build proteins) that plays a central role in the urea cycle. It is produced from arginine by arginase and serves as the acceptor for carbamoyl phosphate to continue the cycle. Urea cycle role: Ornithine + carbamoyl phosphate → citrulline (in mitochondria).
Citrulline exits to cytoplasm, is converted to arginine, which is cleaved to release urea and regenerate ornithine. Ornithine thus cycles continuously, enabling ammonia detoxification. Other functions: Polyamine synthesis - ornithine is the precursor to polyamines (putrescine, spermidine, spermine) via ornithine decarboxylase.
Polyamines are essential for cell growth and function.
Proline synthesis - ornithine can be converted to proline (for collagen) and glutamate. Ornithine supplementation: May reduce fatigue by enhancing ammonia clearance. Combined with arginine for growth hormone stimulation. L-ornithine-L-aspartate used for hepatic encephalopathy.
May improve sleep quality (some studies show reduced cortisol and improved sleep). Ornithine vs arginine: Both support the urea cycle but enter at different points. Ornithine doesn't produce nitric oxide (that's arginine's unique function). Ornithine may be better tolerated in high doses.
Ornithine alpha-ketoglutarate (OKG): Combined supplement used for wound healing and catabolic states. Provides both urea cycle support and Krebs cycle intermediate.
Metabolic Connections
Ornithine connects to 7 other pathways.
Amino Acids
Arginine
Arginine is cleaved by arginase to produce urea and ornithine in the urea cycle
Semi-essential amino acid critical for nitric oxide synthesis, urea cycle function, and creatine production.
Arginine
Arginine is cleaved by arginase to produce urea and ornithine in the urea cycle
Semi-essential amino acid critical for nitric oxide synthesis, urea cycle function, and creatine production.
Citrulline
Ornithine combines with carbamoyl phosphate to form citrulline in the urea cycle
Amino acid that raises arginine levels more effectively than arginine. Supports nitric oxide production and blood flow.
Citrulline
Citrulline is produced from ornithine in the urea cycle
Amino acid that raises arginine levels more effectively than arginine. Supports nitric oxide production and blood flow.
Metabolic Cycles
Urea Cycle
Ornithine is regenerated from arginine and cycles back to accept carbamoyl phosphate
Liver pathway converting toxic ammonia to urea for excretion. Essential for protein metabolism and nitrogen balance.
Urea Cycle
Ornithine is regenerated from arginine and cycles back to accept carbamoyl phosphate
Liver pathway converting toxic ammonia to urea for excretion. Essential for protein metabolism and nitrogen balance.