Occurrence, Biosynthesis and Consequences of Microcystin: A Potent Hepatotoxin of Cyanobacteria
نویسندگان
چکیده
The production of toxin from bloom, scum or mat forming cyanobacteria in fresh, brackish and marine waters is becoming a global issue. The toxins produced comprise mainly hepatotoxins and neurotoxins. Of these toxins microcystin is a cyclic heptapeptide produced by Microcystis, Planktothrix, Anabaena, Nostoc, Hapalosiphon and Anabaenopsis. Microcystins (MCs) comprise more than 80 variants and are highly toxic and inhibit eukaryotic protein phosphatases 1 and 2A activity. Chronic exposure to microcystin causes tumor promotion in human. Microcystins are synthesized nonribosomally via thiotemplate mechanism by microcystin synthetase, encoded by microcystin synthetase gene cluster (mcy). The gene cluster (mcyABCDEFGHIJ) has been cloned and sequenced from Microcystis, Planktothrix and Anabaena. Microcystin is frequently released in water after autolysis of blooms and may impose a risk to human health, when contaminated water is used for drinking purpose. In this review an attempt has been made to assemble all the known information on microcystin.
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