Saxitoxin (STX) is a neurotoxin produced by certain toxic cyanobacteria and dinoflagellates. It is biochemically synthesized by the stepwise involvement of eight core enzymes encoded in sxt genes. Of them, sxtB, a cytidine deaminase (CDA)-like enzyme, may participate in the third step (after sxtA and sxtG) in the toxin synthesis pathway; however, it is insufficiently elucidated in toxic dinoflagellates. In the present study we determined a novel sxtB gene from the STX-producing dinoflagellate Alexandrium catenella, characterized structural motifs and phylogenetic origin, and evaluated transcri...
