Studies on the conversion of paralytic shellfish poison (PSP) components by biochemical reducing agents.

Abstract

By using gonyautoxin-1, 2, 3 (GTX1, 2, 3), which are members of paralytic shellfish poison (PSP), isolated from PSP-infested scallops Patinopecten yessoensis in Funka Bay, Hokkaido, a basic research was made to reveal bioconversion mechanism of PSP components accumulated in bivalves by ingestion of toxic plankton Protogonyaulax tamarensis. The scallops were extracted with acidified ethanol (pH 2.0). The extract was defatted with chloroform, treated with activated charcoal, applied successively to three types of column chromatography on Bio-Gel P-2, Amberlite CG-50 II and Bio-Rex 70. The toxins were finally purified by cellulose acetate membrane electrophoresis. A mixture of GTX1, 2, 3 thus obtained was treated by the methods as described below. A mixture of GTX1, 2, 3 was treated at 37°C for 24 h or 48 h with glutathione (GSH), L-cysteine (L-CySH), flavin adenine dinucleotide (FAD), β-diphosphopyridine nucleotide (β-NAD) and β-diphosphopyridine nucleotide disodium salt (reduced form, β-NAD·2Na) solutions (pH 5.8), respectively. The composition of reaction products obtained was examined by fluorodensitometry. The results were as follows. A mixture of GTX1, 2, 3 (GTX1 : 2%, GTX2 : 71%, GTX3 : 27%) was treated with GSH, to give a mixture of GTX1 (21%), GTX3 (trace) and STX (79%) after 24 h, and to give a mixture of GTX1 (trace), GTX3 (trace) and STX (100%). A mixture of GTX1, 2, 3 as above was treated with L-CySH, to give a mixture of GTX1 (30%), GTX3 (trace) and STX (70%) after 24 h, and to give a mixture of GTX1 (30%), GTX3 (trace) and STX (70%) after 48h. However, GTX1, 2, 3 was not converted to other PSP components by treatment of FAD, β-NAD and β-NAD·2Na. The results obtained here were thought to indicate the possible bioconversion of GTX1, 2, 3 to STX by mild reducing agents such as GSH and L-CySH in vivo.