An exotoxin is a toxin secreted by bacteria. Diphtheria toxin is an exotoxin secreted by "Corynebacterium", the pathogenic bacterium that causes diphtheria. This toxin is a 38 kDa fragment of Pseudomonas exotoxin A. Likewise, "Pseudomonas aeruginosa" exotoxin A inactivates EF-2. The Pseudomonas exotoxin (or exotoxin A) is an exotoxin produced by "Pseudomonas aeruginosa". The exotoxin A of "Pseudomonas aeruginosa" uses a similar mechanism of action. An enterotoxin is a protein exotoxin released by a microorganism that targets the intestines. Also interesting is the effect of alpha-defensins on the exotoxin produced by anthrax ("Bacillus anthracis"). "C. tetani" also produces the exotoxin tetanolysin, a hemolysin, that causes destruction of tissues. Large numbers of "C. perfringens" grow in the intestines, and secrete exotoxin. He also showed that the bacillus produces an exotoxin. Streptococcal pyrogenic exotoxin A ("speA") is probably the best studied of these toxins.