Fostriecin, an antitumor antibiotic with inhibitory activity against serine/threonine protein phosphatases types 1 (PP1) and 2A (PP2A), is highly selective for PP2A

Fostriecin, an antitumor Antibiotic produced by Streptomyces pulveraceus, is a strong inhibitor of type 2A (PP2A; IC50 3.2 nM) and a weak inhibitor of type 1 (PP1; IC50 131 microM) serine/threonine protein phosphatases. Fostriecin has no apparent effect on the activity of PP2B, and dose-inhibition studies conducted with whole cell homogenates indicate that fostriecin also inhibits the native forms of PP1 and PP2A. Studies with recombinant PP1/PP2A chimeras indicate that okadaic acid and fostriecin have different binding sites.