Apolipoprotein B inhibits the hemolytic activity of asp-hemolysin from Aspergillus fumigatus.

We investigated the effect of human blood plasma lipoproteins on the hemolytic activity of Asp-hemolysin. Apolipoprotein B (apoB)-containing lipoproteins, such as low density lipoprotein (LDL) and very low density lipoprotein (VLDL), inhibit the activity of this hemolytic toxin. When Asp-hemolysin (15 mu g) was incubated with 100 mu g LDL (as protein), the hemolytic activity was inhibited by 90%. When 20 mu g apoB was added, the hemolytic activity was almost completely inhibited. Furthermore, similar inhibition was obtained in the filtrates which were separated from the incubation mixture of Asp-hemolysin with LDL or apoB following ultrafiltration through a membrane with a molecular cutoff = 100000. The current findings suggest that the inhibition by LDL is due to apoB binding to Asp-hemolysin.