PP2A inhibition assay using recombinant enzyme for rapid detection of okadaic acid and its analogs in shellfish.

Okadaic acid and its analogs (OAs) responsible for diarrhetic shellfish poisoning (DSP) strongly inhibit protein phosphatase 2A (PP2A) and thus are quantifiable by measuring the extent of the enzyme inhibition. In this study, we evaluated the suitability of the catalytic subunit of recombinant human PP2A (rhPP2Ac) for use in a microplate OA assay. OA, dinophysistoxin-1(DTX1), and hydrolyzate of 7-O-palmitoyl-OA strongly inhibited rhPP2Ac activity with IC(50) values of 0.

The effect of structural variation in 21 microcystins on their inhibition of PP2A and the effect of replacing cys269 with glycine.

Microcystins (MCs) are a group of cyclic heptapeptide hepatotoxins produced by Microcystis and several other genera of cyanobacteria. The representative MC, MC-LR, strongly inhibits protein phosphatase 2A (PP2A), while the inhibitory potencies of at least 60MC analogs characterized from bloom samples and cultured strains have not been fully elucidated. In this study, we determined the IC(50) values for 21MC analogs for inhibiting the recombinant PP2A catalytic subunit (rPP2Ac).

A protein phosphatase 2A (PP2A) inhibition assay using a recombinant enzyme for rapid detection of microcystins.

Worldwide blooms of toxic cyanobacteria (blue-green algae) commonly occur in freshwater, often in drinking water sources, necessitating routine monitoring of water quality. Microcystin-LR and related cyanobacterial toxins strongly inhibit protein phosphatase 2A (PP2A) and are therefore assayable by measuring the extent of PP2A inhibition. In this study, we evaluated the suitability of the catalytic subunit of recombinant PP2A (rPP2Ac) expressed with a baculovirus system for use in a microplate microcystin assay.

Methylation of the C-terminal leucine residue of the PP2A catalytic subunit is unnecessary for the catalytic activity and the binding of regulatory subunit (PR55/B).

Protein phosphatase 2A (PP2A) is composed of structural (A), catalytic (C), and regulatory (B) subunits. The catalytic subunit (PP2A(C)) undergoes reversible carboxyl-methylation and -demethylation at its C-terminal leucine residue (Leu309), catalyzed by PP2A-methyltransferase (PMT) and PP2A methylesterase (PME-1), respectively. In this study, we observed that the activity of PP2A was largely unaffected by the addition of PME-1, and that the regulatory subunit (PR55/B) could bind demethylated PP2A(D).

The primary structure of a hemorrhagic factor, HR2b, from the venom of Okinawa habu (Trimeresurus flavoviridis).

The complete amino acid sequence of a hemorrhagic factor, HR2b, from the venom of Okinawa habu was determined. The hemorrhagic factor was fragmented by CNBr cleavage, trypsin, staphylococcal protease V8 and lysyl endopeptidase digestions. The resulting peptides were purified on high performance chromatography, and sequenced by Edman degradation.