Inactivation of the streptokinase gene prevents Streptococcus equisimilis H46A from acquiring cell-associated plasmin activity in the presence of plasminogen.

The streptokinase gene of Streptococcus equisimilis H46 was inactivated by plasmid insertion mutagenesis to study the relationship between elaboration of streptokinase and acquisition of cell-associated plasmin activity after incubation of wild-type and mutant cells in media containing plasminogen or plasmin. The results showed that H46A binds both the zymogen and active enzyme, generates surface-associated plasmin activity in the presence of plasminogen when producing streptokinase, and expresses its plasmin(ogen) receptor(s) independently of a functional streptokinase gene. At least part of the plasmin(ogen) binding capacity may be due to the glyceraldehyde-3-phosphate dehydrogenase type of receptor molecule, as judged by the detection of the corresponding gene.