Shellfish poisons biosynthesis

Cyanobacterial toxins (both marine and freshwater) are functionally and chemically a diverse group of secondary chemicals. They show structure and function similarities to higher plant and algal toxins. Of particular importance to this publication is the production of toxins which appear to be identical with saxitoxin and neosaxitoxin. Since these are the primary toxins involved in cases of paralytic shellfish poisons, these aphantoxins could be a source of PSP standards and the study of their production by Aphanizomenon can provide information on the biosynthesis of PSP s. The cyanobacteria toxins have not received extensive attention since they have fewer vectors by which they come in contact with humans. As freshwater supplies become more eutrophicated and as cyanobacteria are increasingly used as a source of single cell protein toxic cyanobacteria will have increased importance (39). The study of these cyanobacterial toxins can contribute to a better understanding of seafood poisons. 

Okadaic acid 11 is a potent and specific inhibitor of protein phosphatases produced by the dinoflagellates Prorocentrum lima, Dinophysisfortii, and Dirwphysis accuminata. It accumulates in bivalves and is one of the main toxins responsible for diarrhetic shellfish poisoning (DSP) (11). It has a highly unusual biosynthesis that has generated a lot of speculation because of the presence of isolated acetate chain methyl carbon atoms (10). Okadaic acid is a potent inhibitor of protein phosphatase A (11). 

Saxitoxin (120), a paralytic shellfish poisoning alkaloid, was obtained from cultures of a red tide dinoflagellate Alexandrium sp. The toxin is also used for studies on ion channels. The biosynthesis of saxitoxin (120) involves arginine as a precursor of the guanidinio groups, whereas the perhydropurine skeleton is derived from Claisen condensation of acetate with arginine. The carbon atom in the side chain is derived from Y-adenosyl methionine. " ... 

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