Isolation and properties of gonyautoxin-5,an extremely low-toxic component of paralytic shellfish poison.

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Gonyautoxin-5 (GTX5) was isolated from teh toxic specimens of the oyster Crassostrea gigas collected from Senzaki Prefecture. The digestive glands were extracted with acidic ethanol and the extract was applied successively to activated chaarcoal treatment and three types of chromatography: on Bio-Gel P-2, Amberlite CG-50, and Bio-Rex70. The GTX5 preparation thus obtained was homogeneous in both thin-layer chromatograthy and cellulose acetate membrane electropyoreesis. The specific toxicity was found to be 280 MU/mg, a value which is much lower than that of gonyautoxin-2, or saxitoxin(STX). Howerver, the toxicity of the preparation was increased five times by mild acid-hydrolysis. In the hydrolyzate, STX was found together with two unidentified components. The GTX5 contained approximately one mole of sulfate per molle, and showed a PMR spectrum which is closely similar to that of STX. These results suggest that GTX5 possesses the structure of carbamoyl-N-sulfo-saxitoxin.