Ornithine methyl ester. An unusual metabolite encountered in the urine of patients with a urea cycle disorder characterized by hyperammonemia, hyperornithinemia and homocitrullinuria.

In the urine of six subjects with a urea cycle disorder characterized by hyperammonemia, hyperornithinemia and homocitrullinuria, an unusual ninhydrin-reaction compound was encountered. This unknown on hydrolysis yielded ornithine as the only amino acid and, on dansylation studied, yielded didansyl ornithine. The metabolite from urine has been shown to have the same chromatographic mobility as ornithine methyl ester on paper cellulose thin layer, and ion exchange chromatography. When trimethylsily derivatives were prepared the unknown and the ornithine methyl ester standard had similar mobility on gas chromatography. Identification of the unknown as the ornithine methyl ester was confirmed by gas chromatography-mass spectrometric analysis. In the patients' urines the concentration of methyl ornithine ranged from 70 to 368 microne moles/g creatinine.