Characterization of highly purified native streptokinase and altered streptokinase after alkaline treatment.

Physical and chemical data are reported for highly purified native streptokinase (staphylokinase, EC 3.4.99.22) (Kabikinase) and streptokinase treated with an alkaline agent (altered streptokinase). The mol. wts. were similar and were determined to be 50 200 by sedimentation equilibrium methods, polyacrylamide gradient gel electrophoresis and sodium dodecylsulphate-polyacrylamide gel electrophoresis. The sedimentation coefficient so20,w of native and altered streptokinase was found to be 3.37 S. The frictional ratio and the absorptivity (A1%1cm) at 280 nm of native streptokinase was found to be 1.29 and 7.5, respectively. Native streptokinase showed essentially a single band in the isoelectro-focusing pattern (pI 5.2), while altered streptokinase showed at least two separate bands. Polyacrylamide gel electrophoresis in the presence of Triton X-100 exhibited one band for native streptokinase but altered streptokinase showd two bands. At pH 12 the biological and immunological activity of streptokinase was markedly decreased in a time-dependent reaction. The amino-terminal amino acid of the two streptokinase forms was isoleucine and the carboxyl-terminal amino acid of native streptokinase was tyrosine. Peptide analysis showed that some peptides in altered streptokinase exhibited higher mobility compared to native streptokinase. The data suggest that streptokinase undergoes a conformational change when incubated in alkaline media, but no simultaneous loss of peptides was observed.