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Published on: February 15, 2012
Purification and molecular characterization of subtilisin-like alkaline protease BPP-A from Bacillus pumilus strain
1Department of Food Science and Technology, Faculty of Bioindustry, Tokyo University of Agriculture, Abashiri, Hokkaido, Tokyo, Japan. t-miyaji@bioindustry.nodai.ac.jp
Aims:
The present study was conducted by screening zein-degrading bacteria in an attempt to obtain zein-degrading protease.
Methods And Results:
Soil bacteria were screened by formation of a clear zone on zein plates. Characterization of a zein-degrading bacterium indicated a taxonomic affiliation to Bacillus pumilus, and was named MS-1 strain. The strain produced two different types of extracellular proteases, BPP-A and BPP-B. In this study, we purified and characterized BPP-A because it exhibited a higher ability to hydrolyze zein than BPP-B. When casein was used as the substrate, the optimal pH for BPP-A was 11.0. In BPP-A, zein was better substrate than casein at pH 13.0, whereas casein was better one than zein at pH 11.0. The bppA gene encoded a 383-amino acid pre-pro form of BPP-A, and mature BPP-A contained 275 amino acid residues. It was concluded that BPP-A belonged to the subtilisin family.
Conclusion:
A zein-degrading bacterium assigned to B. pumilus produced two different types of extracellular proteases, BPP-A and BPP-B. BPP-A exhibited an ability to hydrolyze zein in an extreme alkaline condition.
Significance And Impact Of The Study:
This is a first report on screening for zein-degrading micro-organisms. The subtilisin-like protease BPP-A is possible to utilize as an industrial enzyme for the production of zein hydrolysates.
