Isolation of Salmonella typhimurium enterotoxin in partially purified form and study of its properties

S. typhimurium enterotoxin, partially purified in accordance with our scheme (salting out with 75% ammonium sulfate, dialysis and gel filtration in a column with Sephadex G-150, followed by electrofocusing), showed enterotoxic activity in the intestinal loop of a rabbit and yielded the positive result in the cutaneous test. S. typhimurium enterotoxin proved to be protein with a molecular weight of 140000 daltons and the isoelectric point equal to 4.4. The biological activity of S. typhimurium enterotoxin was neutralized with homologous antiserum and with antiserum to cholera enterotoxin. Heating the preparation at 75 degrees C for 30 minutes led to a considerable decrease in its enterotoxic activity.