Inhibition Equivalency Factors for Dinophysistoxin‑1
and Dinophysistoxin‑2 in Protein Phosphatase Assays: Applicability
to the Analysis of Shellfish Samples and Comparison with LC-MS/MS
posted on 2013-03-13, 00:00authored byDiana Garibo, Pablo de la Iglesia, Jorge Diogène, Mònica Campàs
The
protein phosphatase inhibition assay (PPIA) is a well-known
strategy for the determination of diarrheic shellfish poisoning (DSP)
lipophilic toxins, which deserves better characterization and understanding
to be used as a routine screening tool in monitoring programs. In
this work, the applicability of two PPIAs to the determination of
okadaic acid (OA), dinophysistoxin-1 (DTX-1), dinophysistoxin-2 (DTX-2),
and their acyl ester derivatives in shellfish has been investigated.
The inhibitory potencies of the DSP toxins on a recombinant and a
wild PP2A have been determined, allowing the establishment of inhibition
equivalency factors (IEFs) (1.1 and 0.9 for DTX-1, and 0.4 and 0.6
for DTX-2, for recombinant and wild PP2A, respectively). The PPIAs
have been applied to the determination of OA equivalent contents in
spiked and naturally contaminated shellfish samples. Results have
been compared to those obtained by LC-MS/MS analysis, after application
of the IEFs, showing good agreements.