isolation and characterization of thermophilic alkaline proteases resistant to sodium dodecyl sulfate and ethylene diamine tetraacetic acid from bacillus sp. gus1

thermophilic bacillus sp. gus1, isolated from  a soil  sample obtained from citrus garden, produced at least three proteases as detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis (sds-page) and zymogram analysis. the enzymes were stable in the alkaline ph range (8.0-12.0), with the optimum temperature and ph range of the proteases being 70ºc and 6.0-12.0, respectively. all three proteases were also highly stable at 70ºc. after 60 min of incubation at 70ºc, the enzymes retained 100% of their original activities. enzymes were mostly inhibited by phenylmethylsulfonyl fluoride (pmsf), however 80-90% enzyme activities were retained in presence of 2-mercaptoethanol and iodoacetate. addition of sds and ethylene diamine tetraacetic acid (edta) also marginally influenced protease activities, but addition of ca2+ to the proteases did not bring about any change. the results suggeste that most of these proteases were not metalloproteases, but ca2+-independent serine alkaline proteases.