Abstract
The hemolytic active site of Asp-hemolysin from Aspergillus fumigatus was investigated using chemical modification techniques. As amino-terminal residues of Asp-hemolysin, arginine and threonine were detected by the dansyl method. The inhibition reaction with DTNB, 2-PDS, 4-PDS, NQS, TNBS or glyoxal suggested that sulfhydryl and amino group(s) might exist in the hemolytic active site. When one of the three sulfhydryl groups was rapidly modified with DTNB, its hemolytic activity was almost completely lost. The same results were obtained by modification with 2-PDS or 4-PDS, whereas the other two sulfhydryl groups reacted more slowly with DTNB in the presence of 1% SDS or 1N NaOH. The reaction with DTNB or 4-PDS suggested that two sulfhydryl groups were buried in the interior of the toxin molecule and one sulfhydryl group was exposed on the molecule. These findings also suggested that one sulfhydryl group and/or arginine group plays an important role in the hemolytic activity of Asp-hemolysin.
