Delayed skin reactor from streptokinase-streptodornase: stability studies and amino acid analysis.

Delayed skin reactor (DSR), the material in streptokinase-streptodornase responsible for eliciting delayed hypersensitivity reactions in man, is stable as a lyophilized powder or when stored at -70 degrees C. Storage at a pH above or below 6.0 leads to a decrease in the ability of DSR to stimulate lymphocyte proliferation in vitro. Its molecular weight is 30,000 as estimated by sodium dodecyl sulfate gel electrophoresis and it is composed of approximately 260 amino acid residues without apparent sulfhydryl-bridged subunits. The extinction coefficient of DSR (A 1% 280 nm) is 2.6.