Wikipedia
Homocitrulline
L-Homocitrulline is an amino acid and a metabolite of ornithine in human metabolism and mammalian. The amino acid can be detected in larger amounts in the urine of individuals with urea cycle disorders. At presence, 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.