Abstract
One lethal factor in the skin secretion from the oriental catfish Plotosus lineatus was purified successively by DEAE-cellulose, CM-cellulose and Sephadex G-75 and its homogeneity was sup-ported by analytical disc electrophoresis. The purified lethal factor had a LD50 of 0.71mg/kg (intravenous injection into mice). In addition, it exhibited a strong edema-forming activity; the minimum edema dose inducing 130% edema ratio was as small as 0.89μg. The molecular weight was estimated to be 11, 000 by gel filtration on Sephadex G-75. Unexpectedly the molecular weight determination by SDS disc electrophoresis was unsuccessful because no band was detected under the various tried conditions. Although the purified lethal factor was a basic protein, it was richer in acidic amino acids than basic amino acids, indicating that the acidic amino acids exist in the molecule as an amide form.
