title: Studies on the toxin of Aspergillus fumigatus. XVIII. Photooxidation of asp-hemolysin in the presence of various dyes and its relation to the site of hemolytic activity.
abstract: The site of hemolytic activity of a toxin isolated from Aspergillus fumigatus designated Asp-hemolysin was determined by photooxidation techniques. The hemolytic activity of this toxin was strongly inhibited by photooxidation with methylene blue, rose bengal, riboflavin, or eosin G as a sensitizer, whereas crystal violet, hematoxylin, naphthol yellow S, bromothymol blue, methyl orange, and cresol red had no effect. pH dependence of the inactivation with methylene blue was observed in the narrow range of pH values from 7.0 to 8.0, like that of the inactivation with rose bengal or riboflavin. The histidine, cysteine, methionine, tryptophan, and tyrosine content of methylene blue-photooxidized Asp-hemolysin was significantly decreased, while other amino acids were not affected. The hemolytic activity of the toxin was lost more slowly than the histidine residue, being maintained at about 50% even at the time when the histidine residue was completely lost after 30 min. Photooxidation of Asp-hemolysin in the presence of rose bengal also caused a decrease in histidine, methionine, and threonine content. These findings suggest that residues of cysteine, methionine, threonine, tryptophan, and/or tyrosine but not histidine may play an important role through stereostructure in the manifestation of the hemolytic activity of Asp-hemolysin.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001232:Aspergillus fumigatus / Q000032:analysis*; D004396:Coloring Agents; D006460:Hemolysin Proteins / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D009183:Mycotoxins / Q000302:isolation & purification*; D010777:Photochemistry; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D004396:Coloring Agents; D006460:Hemolysin Proteins; D009183:Mycotoxins