A sensitive ELISA for serum ornithine carbamoyltransferase utilizing the enhancement of immunoreactivity at alkaline pH

BackgroundWe developed a new enzyme-linked immunosorbent assay (ELISA) for ornithine carbamoyltransferase (OCT) and evaluated its usefulness.MethodsRecombinant human OCT expressed in E. coli was used as an antigen to obtain the monoclonal antibodies for this assay.ResultsThe reactivity of the antibodies to native OCT as well as recombinant OCT was enhanced at alkaline pH (8.5–10), and the assay's sensitivity was markedly improved. The antibodies react identically with native and recombinant OCT at pH 9.4. The dilution test showed a good linearity between dilution ratios and the concentrations. Different concentrations of OCT added were recovered on average at 90.4%. There was a good correlation between OCT protein levels in the ELISA and OCT enzyme activities (r = 0.987, p < 0.0001). A significant difference in the serum level of OCT was observed between chronic hepatitis patients (110.7 ± 80 ng/ml) and healthy subjects (34.4 ± 20.7 ng/ml) (p < 0.0001). The serum levels of OCT between sexes differed significantly in the healthy subjects (p < 0.0001).ConclusionsOur newly established ELISA for OCT using monoclonal antibodies is sensitive enough for clinical application.