Studies on the Toxin of Aspergillus fumigatus

Abstract

A hemolytic toxin has been obtained from mycelia and culture filtrates of Aspergillus fumigatus by the procedures that included precipitation with ammonium sulfate, chromatography of DEAE‐Sephadex, affinity chromatography on Concanavalin A‐Sepharose and gel filtration on Sephadex G‐50, G‐100 and G‐150. The purified homolytic toxin was homogeneous on immunological and disk electrophoretic analysis, and the toxin from culture filtrates was identical with that from mycelia by the immunodiffusion technique. The hemolytic toxin was obtained for the first time from fungi and designated as Asp‐hemolysin. The molecular weight of Asp‐hemolysin was estimated to be approximately 30,000 by the gel‐filtration technique and its isoelectric point was found to be around pH 4.0. This Asp‐hemolysin contained large amounts of protein and very small amounts of carbohydrate. The UV absorption spectrum of Asp‐hemolysin showed a maximum absorption at 280 nm and minimum absorption at 251 nm. The extinction coefficient at 280 nm, E ^1%_1cm, was 12.4 and the ratio of absorbance at 280 nm to that at 260 nm was 2.3. The optimum pH for the hemolytic activity of the toxin toward chicken erythrocytes was 5.0 at room temperature and it was active in the pH range of 3.5 to 10.5. The optimum temperature was 21 C and about 50% of the activity was lost by incubation at 50 C for 5 min or 45 C for 23 min. The hemolytic activity was remarkably inhibited by Hg²⁺, Cu²⁺, Fe²⁺, Ag¹⁺, iodine and p‐CMB, but enhanced slightly by Zn²⁺ and Co²⁺.