Enhanced activation of bound plasminogen on Staphylococcus aureus by staphylokinase

Activation of plasminogen (pig) to plasmin by the staphylococcal activator, staphylokinase (SAK), is effectively regulated by the circulating inhibitor, alpha(2)-antiplasmin (alpha(2)AP). Here it is demonstrated that intact Staphylococcus aureus cells and solubilized staphylococcal cell wall proteins not only protected SAK-promoted pig activation against the inhibitory effect of alpha(2)AP but also enhanced the activation. The findings suggest that the surface-associated pig activation by SAK may have an important physiological function in helping staphylococci in tissue dissemination. Amino acid sequencing of tryptic peptides originating from the 59-, 56- and 43-kDa proteins, isolated as putative plg-binding proteins, identified them as staphylococcal inosine 5'-monophosphate dehydrogenase, a-enolase, and ribonucleotide reductase subunit 2, respectively. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.