Preparation and Properties of a Vi Antigen-Degrading Enzyme

Baker, Edgar E. (Boston University School of Medicine, Boston, Mass.), and Roberta E. Whiteside . Preparation and properties of a Vi antigen-degrading enzyme. J. Bacteriol . 89: 1217–1224. 1965.—Vi antigen can be hydrolyzed by an inducible enzyme produced by a microorganism isolated from soil. The organism can be identified as Bacillus sphaericus . The enzyme in the culture supernatant fluid can be concentrated and partially purified by precipitation with ammonium sulfate at 50% of saturation. The partially purified enzyme is relatively stable. Incubation of the enzyme with Vi antigen causes a rapid loss of serological activity, a decrease in viscosity, the loss of ability to precipitate albumin at p H 4.0, and the production of reducing sugar and hexosamine. Optimal conditions for enzyme action on Vi antigen are p H 8.4 and 40 C. The reaction rate is independent of the substrate concentration. Intact protein and calcium activates the Vi antigen-enzyme system. The enzyme is not inhibited by its reaction products.