Sulfotransferase （ST） is the first enzyme discovered in association with paralytic shellfish poisoning （PSP） toxin biosynthesis in toxic dinoflagellates. This study investigates the ST activity m crude enzyme extraction of a toxic dinoflagellate species, Alexandrium tamarense CI01. The results show that crude enzyme can transfer a sulfate group from 3＇-phosphoadenosine 5＇-phosphosulfate （PAPS） to N-21 in the carbamoyl group of gonyautoxin 2/3 （GTX2/3） to produce C 1/C2, but is inactive toward STX to produce GTX5. The crude enzyme is optimally active at pH 6.0 and 15℃. The activity is enhanced by Co^2＋, Mg^2＋, Mn^2＋ and Ca^2＋ individually, but is inhibited by Cu^2＋. Moreover, the activity shows no difference when various sulfur compounds are used as sulfate donors. These results demonstrate that the ST specific to GTX2/3 is present in the cells of A. tamarense CI01 and is involved in PSP toxin biosynthesis. In addition, the ST from different dinoflagellates is species-specific, which explains well the various biosynthesis pathways of the PSP toxins in toxic dinoflagellates.
