Intrinsic and chemically produced microheterogeneity of Staphylococcus aureus enterotoxin type C

Staphylococcus aureus enterotoxins C1 (SEC1) and C2 (SEC2) produced from 50-liter quantities of crude culture supernatants were purified chromatographically in a neutral or acid milieu. Microheterogenity of SEC1 was markedly increased by treatment of the purified toxin with alkali, and new more acidic charged species appeared. SEC2 was more heterogenous than any of the other S. aureus enterotoxins and was affected only slightly by treatment with alkali. Prolonged incubation of the organism during production of the SEC2 produced changes in charged species that may be related to a bacterial deamidase, since similar changes were not seen with alkaline treatment of the purified toxin. Although SEC1 and SEC2 showed complete identity immunologically, they are separate, distinct toxins, and alkali treatment of SEC1 did not produce SEC2.