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Abstract
A sensitive enzyme immunoassay (EIA) was developed for the determination of ornithine decarboxylase (ODC, EC 4.1.1.17), in the range of 0.02–10 ng, using an affinity-purified anti-ODC-Fab'-peroxidase conjugate. The amount of ODC protein was determined in crude extracts from the kidney of testosterone-treated mice, regenerating rat liver and human thyroid carcinoma, with purified mouse kidney or rat liver enzyme as standard. In all these tissues, similar activity/protein ratios were found for ODC: 1.2 × 106−1.9 × 106 nmol CO2/h/mg of ODC protein, which were roughly equivalent to the final specific activity of purified enzymes. ODC inactivated by α- difluoromethylornithine (DFMO) could also be assayed with this method similarly to active ODC protein. However, ODC-antizyme complex gave a somewhat lower value than free ODC protein.