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Toxicon. 1992 Aug;30(8):873-8.

Structurally different members of the okadaic acid class selectively inhibit protein serine/threonine but not tyrosine phosphatase activity.

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Cancer Prevention Division, National Cancer Center Research Institute, Tokyo, Japan.


The relative potencies of four main types of okadaic acid class compounds as inhibitors of the catalytic subunits of protein serine/threonine phosphatases 1 and 2A and the protein tyrosine phosphatase 1 were determined. These four types of compounds are okadaic acid, calyculin A, microcystin-LR, and tautomycin, which are isolated from different natural sources, a black sponge Halichondria okadai, a marine sponge Discodermia calyx, a blue-green alga Microcystis aeruginosa, and Streptomyces spirover ticillatus, respectively. While okadaic acid was a more effective inhibitor of protein phosphatase 2A (IC50, 0.07 nM) than protein phosphatase 1 (IC50, 3.4 nM), other compounds of the okadaic acid class were equally effective against the two protein serine/threonine phosphatases. The order of potency was microcystin greater than calyculin A greater than tautomycin, and the IC50S ranged from 0.1 to 0.7 nM. None of the okadaic acid class compounds inhibited protein tyrosine phosphatase 1 activity at concentrations up to 0.01 mM. These results indicate that the compounds of the okadaic acid class are selective inhibitors of protein serine/threonine but not tyrosine phosphatases.

[Indexed for MEDLINE]

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