Recombinant Staphylococcus phage 42D protein (sak) (Active)

Staphylokinase activates plasminogen into plasmin through a unique cofactor mechanism distinct from mammalian plasminogen activators, making it a valuable tool for studying fibrinolytic pathways and thrombolytic drug development. This tag-free recombinant form, covering residues 28–163 of the mature protein, preserves an unobstructed active site and demonstrates a specific activity of 5.0 × 10⁴ IU/mg as measured by fibrin lysis in an agarose plate assay—providing a quantitative benchmark suitable for kinetic parameter analysis (Km, Vmax, kcat), inhibitor screening with IC50 determination, and use as a positive control in plasminogen activation assays. The absence of fusion tags eliminates steric interference that could confound substrate specificity profiling or crystallographic studies. Purity exceeding 97% by SDS-PAGE combined with endotoxin levels below 1.0 EU/μg satisfies the criteria typical for accurate enzyme kinetics and cell-based fibrinolysis experiments where endotoxin contamination would compromise results.