A sensitive enzyme-linked immunosorbent assay of serum ornithine carbamoyltransferase

Ornithine carbamoyltransferase (OCT), a urea cycle enzyme, is located almost exclusively in liver mitochondria. We designed a sensitive enzyme-linked immunosorbent assay (ELISA) of serum OCT protein using an antibody against purified bovine enzyme. OCT protein measured using this method showed a good correlation with OCT activity (r = 0.961), and was much higher in patients with liver diseases than in the controls. Measurements of serum OCT protein in 442 healthy blood donors gave the upper limit of normal range of 23 ng Eq/ml (equivalent to the bovine enzyme) for males, 8 ng Eq/ml for females, and 16 ng Eq/ml for males plus females. The values differ significantly between the sexes and depending on ages. This ELISA system is expected to be used as a pertinent liver function test.