Lysosomal Catabolism of a Protein Toxin: Staphylococcal Enterotoxin B
ARMY MEDICAL RESEARCH INST OF INFECTIOUS DISEASES FORT DETRICK MD
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Lysosomal proteases of rabbit liver, kidney and polymorphonuclear cells were tested for their ability to hydrolyze staphylococcal enterotoxin B, a protein exotoxin of Staphylococcus aureus. All lysosomal preparations effectively inactivated and catabolized staphylococcal enterotoxin B in vitro, but only at pH values less than 3.2 and coincident with acid denaturation of toxin. Minimal digestion of staphylococcal enterotoxin B without loss of biological properties was observed at lower H concentrations. Denaturation of toxin by heating or performic acid oxidation markedly increased the pH range as well as the extent to which staphylococcal enterotoxin B was hydrolyzed. Iodination of staphylococcal enterotoxin B by either a chloramine T or a modified enzymatic method yielded derivatives which were more resistant to lysosomal digestion than the unmodified molecule. These results suggest that modification of a proteins native structure may either increase decrease its susceptibility to digestion by lysosomal proteases.