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 pH 4.0, and the production of reducing sugar and hexosamine. Optimal conditions for enzyme action on Vi antigen are pH 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.