Proteolysis of Clostridium perfringens type A enterotoxin during purification

The small satellite bands of enterotoxin frequently seen in polyacrylamide gels following purification of Clostridium perfringens enterotoxin were found to be due to endogenous protease activity and were not present if phenylmethylsulfonyl fluoride (PMSF; 1 mM) and EDTA (10 mM) were used in the purification protocol. The use of PMSF was avoided by passing gel filtration-purified enterotoxin material through DEAE-Sephacel. This modified protocol resulted in an 11.4-fold purification of enterotoxin and a 26.8% yield. Contrary to previous reports (B. R. Dasgupta and M. W. Pariza, Infect. Immun. 38: 592-597, 1982), if PMSF and EDTA were included during purification, we were unable to detect the novel enterotoxin ET-1 produced by strain NCTC 10240. C. perfringens proteases cleaved homogeneous enterotoxin into two additional fragments, suggesting that ET-1 was a product of endogenous protease action during purification.