Evaluation of protein phosphatase 2A (PP2A) inhibition assay for rapid detection of DSP toxins in scallop

Diarrhetic shellfish poisoning (DSP) refers to a gastrointestinal disease following the ingestion of bivalve shellfish containing dinoflagellate toxins of lipophilic nature collectively referred to as okadaic acids (OAs). OAs strongly inhibit protein phosphatase 2A (PP2A) and thus are quantifiable by measuring the extent of the enzyme inhibition. We recently produced the recombinant catalytic subunit of human PP2A (rhPP2Ac) by genetic engineering techniques using the baculovirus expression system with High Five insect cells. In this study, we evaluated the suitability of rhPP2Ac for use in a microplate OA assay. The limits of detection and quantitation for OA in the whole meat of the scallop Patinopecten yessoensis were 0.0262 mg/kg and 0.0470 mg/kg respectively, which are well below the regulation level in Japan (0.16 mg/kg whole meat). Differences in lipid content of the scallop did not affect the measurement result. Our results confirm that the assay kit using rPP2Ac is an excellent tool for detecting and quantifying OAs in shellfish.