Cloning, expression, and fibrin (ogen)olytic properties of a subtilisin DJ-4 gene from Bacillus sp. DJ-4

Previously, we purified a strong fibrinolytic enzyme (subtilisin DJ-4) from Bacillus sp. DJ-4 and characterized its enzymatic activity. Here, we cloned the gene subtilisin DJ-4, and determines its nucleotide sequence, which showed 97% identity with subtilisin BPN' from B. amyloliquefacens. Recombinant full-subtilisin DJ-4 (rf-subDJ-4) and mature-subtilisin DJ-4 (rm-subDJ-4) were expressed using a pET29 vector system, and their fibrin (ogen)olytic and plasminogen activator activities were studied. rf-subDJ-4 was found to have a higher stability to heat (60 degrees C) and to acidic conditions (pH 3.0-4.0) than the native subtilisin DJ-4 of Bacillus sp. DJ-4. The plasminogen activator activity of rf-subDJ-4 was 2.75 times greater than that of plasmin on a molar basis. And its specific activity (F/C, the ratio of fibrinolytic activity to caseinolytic activity) was 2.67 and 3.97 times higher than those of subtilisin BPN' and subtilisin Carlsberg, respectively. rf-subDJ-4 rapidly hydrolyzed the Aalpha-, Bbeta-, and gamma-chains of fibrinogen within 5 min. But, unlike subtilisin BPN' at a very low concentration (50 ng), the gamma-chain was not cleaved. On the other hand, rm-subDJ-4 did not show enzyme activity.