IDENTIFICATION AND CHARACTERIZATION OF A TYPE-1 PROTEIN PHOSPHATASE FROM THE OKADAIC ACID-PRODUCING MARINE DINOFLAGELLATE PROROCENTRUM-LIMA

The unicellular marine dinoflagellate, Prorocentrwn lima, an establish ed producer of okadaic acid (OA), was shown to contain a type-1 protei n phosphatase (PP-1) the biochemical profile of which on Mono-Q and Su perdex-75 fast protein liquid chromatography was identical to the cata lytic subunit of PP-1 from rabbit skeletal muscle. Purified P lima PP- 1 (apparent molecular mass 37.5 kDa) was highly sensitive to inhibitio n by mammalian protein phosphatase inhibitor-1 and inhibitor-2, and to OA itself. A 6-7-fold increase in OA production by P lima, when grown under controlled conditions, correlated with an up to 300-fold increa se in P. lima PP-1 activity. Furthermore, P. lima did not contain any detectable type-2A protein phosphatase activity. This study represents the first identification of a serine/threonine protein phosphatase in a dinoflagellate.