Homocitrulline

L-Homocitrulline is an amino acid and a metabolite of ornithine in mammalian (including human) metabolism. The amino acid can be detected in larger amounts in the urine of individuals with urea cycle disorders. At present, it is thought that the depletion of the ornithine supply causes the accumulation of carbamyl-phosphate in the urea cycle which may be responsible for the enhanced synthesis of homocitrulline and homoarginine. Both amino acids can be detected in urine. Amino acid analysis allows for the quantitative analysis of these amino acid metabolites in biological fluids such as urine or blood. L-Homocitrulline is an amino acid and a metabolite of ornithine in mammalian (including human) metabolism. The amino acid can be detected in larger amounts in the urine of individuals with urea cycle disorders. At present, it is thought that the depletion of the ornithine supply causes the accumulation of carbamyl-phosphate in the urea cycle which may be responsible for the enhanced synthesis of homocitrulline and homoarginine. Both amino acids can be detected in urine. Amino acid analysis allows for the quantitative analysis of these amino acid metabolites in biological fluids such as urine or blood. Homocitrulline is one methylene group longer than citrulline, but similar in structure. The metabolite is generated from a lysine residue after lysine reacts with cyanate. Cyanate is present in the human body in equilibrium with urea. Under physiological conditions the urea concentration may be too low to allow extensive carbamylation. However, the conversion process leading to the formation of homocitrulline from lysine in proteins is known to occur in vivo. During renal failure conditions, the urea concentration increases and carbamylation of many proteins can occur, which can be detected. It is believed that most carbamylation takes place during inflammation when the enzyme myeloperoxidase is released from neutrophils. This enzyme converts thiocyanate to cyanate. Increased levels of cyanate can now carbamylate lysine residues.