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  • Title: Inhibition of protein phosphatases-1 and -2A with acanthifolicin. Comparison with diarrhetic shellfish toxins and identification of a region on okadaic acid important for phosphatase inhibition.
    Author: Holmes CF, Luu HA, Carrier F, Schmitz FJ.
    Journal: FEBS Lett; 1990 Sep 17; 270(1-2):216-8. PubMed ID: 2171991.
    Abstract:
    Acanthifolicin (9,10-epithio-okadaic acid from Pandoras acanthifolium) inhibited protein phosphatase-1 (PP1) similarly to okadaic acid (IC50 = 20 nM and 19 nM, respectively) but was slightly less active against protein phosphatase-2A (PP2A) (IC50 = 1 nM and 0.2 nM, respectively). Methyl esterification of acanthifolicin sharply reduced its activity. PP2A was inhibited with an IC50 = 5.0 microM, whilst PP1 was inhibited less than 10% at 250 microM toxin. Okadaic acid methyl ester was similarly inactive whereas dinophysistoxin-1 (35-methyl okadaic acid) inhibited PP1/2A almost as potently as okadaic acid. Pure acanthifolicin/okadaic acid methyl ester may be useful as specific inhibitors of PP2A at 1-10 microM concentrations in vitro and perhaps in vivo. The data also indicate that a region on these toxins important for PP1/2A inhibition comprises the single carboxyl group.
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