A protein phosphatase 2A inhibition assay for a fast and sensitive assessment of okadaic acid contamination in mussels.

The specific inhibitory activity exerted by okadaic acid on protein phosphatase 2A was used to assess the presence of okadaic acid in mussels, using a commercially available protein phosphatase 2A preparation. Under the conditions used, okadaic acid inhibits the enzymatic activity dose-dependently, with an IC50 = 0.26 ng/ml (0.32 nM). The assay is accurate and reproducible. Okadaic acid was detected in concentrations as low as 0.063 ng/ml in aqueous solutions and 2 ng/g in mussel digestive glands. Thirty naturally contaminated mussel samples were submitted to the protein phosphatase 2A inhibition assay as well as to an ELISA assay and to a MTT cytotoxicity assay, with similar results. The proposed assay is sensitive, rapid and does not require expensive equipment. These characteristics make it a good candidate for employment in the routine assessment of okadaic acid shellfish contamination.