FR225659-binding proteins: identification as serine/threonine protein phosphatase PP1 and PP2A using high-performance affinity beads.

FR225659 was originally isolated as a novel gluconeogenesis inhibitor produced by fungal strain Helicomyces sp. No. 19353. To identify the target protein of FR225659, we synthesized high-performance affinity latex beads that immobilized FR225659 derivative FR253761 or FR259383. Using these beads, we identified FR225659 binding proteins as serine/threonine protein phosphatase type1 (PP1) and type2A (PP2A) from rat hepatocyte crude extract. FR225659 and its synthetic derivatives were strongly inhibited the enzyme activities of purified catalytic subunits of PP1 and PP2A in vitro.