Ohchinolide B

Okadaic acid, a marine toxin, is an inhibitor of protein phosphatases (PP). Okadaic acid has a significantly higher affinity for PP2A (IC50=0.1-0.3 nM), and inhibits PP1 (IC50=15-50 nM), PP3 (IC50=3.7-4 nM), PP4 (IC50=0.1 nM), PP5 (IC50=3.5 nM), but does not inhibit PP2C. Okadaic acid increases of phosphorylation of a number of proteins by inhibiting PP, and acts a tumor promoter. Okadaic acid induces tau phosphorylation[1][2].