Purification and characterization of a novel high molecular weight exotoxin produced by red tide phytoplankton, Alexandrium tamarense

J Biochem Mol Toxicol. 2008 Nov-Dec;22(6):405-15. doi: 10.1002/jbt.20253.


Our recent studies have demonstrated that the aqueous extract prepared from Alexandrium tamarense, a harmful red tide phytoplankton, showed cytotoxicity on Vero cells. In this study, the toxic substance was purified from the culture supernatant of A. tamarense. Based on the gel-filtration profile, the molecular mass of a purified toxin was estimated to be about 1,000 kDa. On sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, a main band with molecular mass of 1,000 kDa was detected with periodic acid-Schiff (PAS) staining, but no protein bands were detected by Coomassie brilliant blue (CBB) protein staining. Sugar composition analysis of the toxin suggested that the toxin contains galactose, fucose, mannose, N-acetylglucosamine, xylose, and other minor saccharides, whereas no significant levels of amino acids were detected by amino acid analysis. These results suggest that the toxin is a polysaccharide-based compound. The toxin showed cytotoxic effects on various cell lines in a concentration-dependent manner. Among the cell lines tested, U937 cells were the most susceptible to the toxin. In U937 cells treated with the toxin, a typical apoptotic nuclear morphological change and DNA fragmentation were observed. This is the first report demonstrating that a polysaccharide-based toxin isolated from red tide phytoplankton can induce apoptotic cell death.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Death / drug effects
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Cell-Free System
  • Cells, Cultured
  • Chlorocebus aethiops
  • Chromatography, Gel
  • Chromatography, High Pressure Liquid
  • DNA Fragmentation / drug effects
  • Dinoflagellida / chemistry*
  • Dinoflagellida / cytology
  • Enzyme Inhibitors / pharmacology
  • Exotoxins / chemistry
  • Exotoxins / isolation & purification*
  • Exotoxins / metabolism*
  • Exotoxins / pharmacology
  • HeLa Cells
  • Hemolysis / drug effects
  • Humans
  • Molecular Weight
  • Phytoplankton / chemistry*
  • Phytoplankton / cytology
  • Polysaccharides / chemistry
  • Rabbits
  • Subcellular Fractions / drug effects
  • Subcellular Fractions / metabolism
  • U937 Cells
  • Vero Cells


  • Enzyme Inhibitors
  • Exotoxins
  • Polysaccharides