IDENTIFICATION OF PROTEIN PHOSPHATASE INHIBITORS OF THE MICROCYSTIN CLASS IN THE MARINE-ENVIRONMENT

Toxins produced by marine phytoplankton represent a severe global heal th hazard to humans that eat seafood and are also responsible for mass ive natural fish kills in specialized bloom situations. Tumour-promoti ng hepatotoxins from the freshwater microcystin/nodularin class were i dentified in Northeastern Pacific Ocean, Eastern Canadian and European mussels for the first time. These hepatotoxins were detected at biolo gically active levels up to three-fold higher than accepted quarantine levels for the diarrhetic shellfish toxin okadaic acid (OA), based on their activity (in microcystin-LR equivalent units) in a liquid chrom atography (LC)-linked protein phosphatase bioassay. The presence of mi crocystins/nodularins in oceanic shellfish identifies a potentially no vel class of intoxication which is also prevalent in other forms of ma rine aquatic life, namely sponges and fish. The widespread presence of prokaryotic microcystins and nodularins in the marine environment may be indicative of the importance of signal transduction pathways invol ving potent inhibition of protein phosphatases in early marine eukaryo tes.