Screening of strains identified as extremely thermophilic bacilli for extracellular proteolytic activity and general properties of the proteinases from two of the strains

• Published in: Journal of Applied Bacteriology
• Main Authors: Coolbear, T., Eames, C.W., Casey, Y., Daniel, R.M., Morgan, H.W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1991
• Subjects: New Zealand; Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1111/j.1365-2672.1991.tb04456.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2672.1991.tb04456.x; http://onlinelibrary.wiley.com/wol1/doi/10.1111/j.1365-2672.1991.tb04456.x/fullpdf

T. COOLBEAR, C.W. EAMES, Y. CASEY, R.M. DANIEL AND H.W. MORGAN. 1991. Forty‐one strains isolated from thermal areas in New Zealand, Fiji and Antarctica were shown to be extremely thermophilic Bacillus spp. (growth optima > 65 . C) by comparison with reference strains with a series of standard tests. Some morphological and physiological variation between strains was noted. Various assay procedures were employed to assess the strains for their ability to produce extracellular proteolytic activity. The strain EA. 1 gave the highest yield of proteolytic activity under the conditions imposed. A second strain, OK3A.1, also gave high yields of activity but differed from the EA.1 activity in that it was more tolerant to both high pH and EDTA. The proteinases from these two strains were purified and characterized. Maximum activity was given by EA.1 proteinase over a narrow pH range with an optimum at pH 6.7 and 50% activity limits at pH 5.6 and 7.5. OK3A.1 had a similar pH optimum but was active over a broader range with 50% activity limits at pH 5.2 and 8.5. Both enzymes were endo‐acting proteinases; neither showed activity against two small synthetic peptides. By SDS‐polyacrylamide gel electrophoresis the molecular masses for EA.1 proteinase and OK3A.1 proteinase were 42 000 Da and 32 000 Da respectively. Both enzymes were resistant to 10 mmol/1 phenylmethylsulphonylfluoride and iodoacetic acid, but were deactivated by EDTA. Whereas EA.1 proteinase was inhibited by o ‐phenanthroline and activated by zinc ions, OK3A.1 proteinase was unaffected by either agent although some dependence on divalent metal ions for activity was apparent. The enzymes were stabilized by calcium ions, EA.1 proteinase exhibiting a half‐life of 2 h at 85.C whilst OK3A.1 proteinase was less stable with a half‐life of 40 min at this temperature.