ISOLATION AND IDENTIFICATION OF THE FAST-DEATH FACTOR IN MICROCYSTIS AERUGINOSA NRC-1

Abstract

The fast-death factor in Microcystis aeruginosa NRC-1 is an acidic, probably cyclic peptide containing the following amino acids in the molar ratios indicated: L-aspartic (1); L-glutamic (2); D-serine (1); L-valine (1); L-ornithine (1); L-alanine (2); L-leucine (2). It is possible, although not likely, that one of the residues of glutamic, alanine, or leucine also is in the D-configuration. The toxin, in the form of its sodium salt, was extracted from lyophilized algal cells by water, separated from pigments by extraction into n-butanol, and freed from high-molecular-weight impurities by dialysis. No separation of a single toxic compound could be obtained by countercurrent distribution, chromatography, or electrophoresis in carbonate, acetate, or phosphate buffers. Electrophoresis of the crude toxin on cellulose in 0.1 M borate yielded five peptides one of which was toxic and accounted for 100% of the toxicity present in the crude preparation. The intraperitoneal LD₅₀of the pure toxin for mice was 0.466 ± 0.013 mg/kg body weight.