1. An enzyme system that catalyses the sulphation of p-nitrophenol, cholesterol, α-ecdysone, β-sitosterol, dehydroepiandrosterone, oestrone and four other steroids of plant and insect origin was obtained from the soluble fraction of southern-armyworm gut tissues. 2. The enzyme system required ATP and inorganic sulphate, and activity was slightly enhanced in the presence of GSH. 3. The properties of this enzyme system with respect to pH, temperature, substrate and protein concentrations and various cofactors and reagents were studied. At −23°C the enzyme preparation could be stored for 2 weeks without drastic loss of activity. At the end of storage for 1 month the loss of activity was approx. 21%. 4. The possible involvement of this enzyme system in insect endocrine control is discussed.
