A novel method for measuring serum ornithine carbamoyltransferase

Background: Serum ornithine carbamoyltransferase is a diagnostic marker of hepatic disorders due to its localization in periportal mitochondria. Methods: We have developed a new method for the determination of serum ornithine carbamoyltransferase. It is based on the reverse reaction of ornithine carbamoyltransferase, using ornithine-ketoacid aminotransferase, Δ¹-pyrroline-5-carboxylate dehydrogenase and glutamate dehydrogenase, which together convert citrulline through ornithine to glutamate. The glutamate is then quantitatively measured using glutamate oxidase and Trinder's reagent. Results: The results obtained by this method agreed well with those obtained using the diacetylmonoxime method as a gold standard [correlation coefficient (r) = 0.973 P<0.001]. The endogenous amino acids sensitive to this method in serum (glutamate, ornithine and Δ¹-pyrroline-5-carboxylate) were eliminated by the initial futile reaction. The new method appears to be more accurate at low levels of ornithine carbamoyltransferase activity than the diacetylmonoxime method. Conclusions: Here we report a new method for serum ornithine carbamoyltransferase assay which might be useful for clinical diagnosis of hepatic disorders, including hepatic cancer.