1984 Volume 5 Issue 2 Pages 125-134
We have developed an enzyme immunoassay (EIA) system (‘sandwich method’) for a flavoenzyme, D-amino acid oxidase (DAO), employing polystyrene beads as a solid-phase, and Fab’-horseradish peroxidase conjugate. This assay system is accurate and precise in the concentration range of 1.0—100 ng/ml, and up to 26 h at 4°C. At 37°C, the measurable DAO concentration range is considerably decreased. DAO and quasi D-amino acid oxidase (Quasi-DAO) completely crossreacted with the anti-DAO antibody both in the double immunodiffusion test, and in the assay with the EIA system. The system is therefore useful for measuring the total content of DAO and Quasi-DAO. The DAO content in crude samples such as the kidney homogenate and serum can be accurately measured. In hog serum, DAO was not detectable; in hog kidney cortex extract, DAO was estimated to be 2.2 ± 0.6 μg/mg protein. DAO was irreversibly polymerized on iodination by the chloramine T method, and the nonspecific counts were very high, which caused our inability to use a radioimmunoassay in the determination of DAO.
