ENGINEERING AND PRODUCTION OF STREPTOKINASE IN A BACILLUS-SUBTILIS EXPRESSION-SECRETION SYSTEM

Streptokinase is one of the major blood-clot-dissolving agents used in many medical treatments. with the cloned streptokinase gene (skc) ava ilable, production of the secreted streptokinase from various Bacillus subtilis strains was studied. The use of the six-extracellular-protea se-deficient strain, WB600, greatly improved the production yield of t he secreted streptokinase. A modified skc which has the original skc p romoter and signal sequence replaced,vith the B. subtilis levansucrase promoter and signal sequence was also constructed. B. subtilis carryi ng either the wild-type or the modified skc produces streptokinase at a comparable level. Even with WB600 as the expression host, a C-termin ally-processed streptokinase was also observed. Through region-specifi c combinatorial mutagenesis around the C-terminal processing sites, st reptokinase derivatives resistant to C-terminal degradation were engin eered. One of the derivatives showed a 2.5-fold increase in specific a ctivity and would potentially be a better thrombolytic agent.