Purification and characterization of extracellular alkaline serine protease from Stenotrophomonas maltophilia strain S-1.
OBJECTIVE
The present study was conducted by screening soil bacteria in an attempt to isolate a bacterium that produced extracellular alkaline protease, and for purification and characterization of the protease.


RESULTS
Soil bacteria were screened by growth on casein as the sole carbon source. Characterization of a strain isolated from soil of Abashiri, Japan indicated a taxonomic affiliation to Stenotrophomonas maltophilia, and was named S-1 strain. The purified S-1 protease, designed S. maltophilia Protease-1 (SmP-1), exhibited an optimal pH of 12.0, optimal reaction temperature of 50 degrees C and a molecular mass of approximately 40 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The cleavage sites of the oxidized-insulin B chain by SmP-1 were identified as Leu6-Cys7, Cys7-Gly8, Tyr16-Leu17 and Leu17-Val18. The N-terminal amino acid sequence of the purified alkaline protease was determined as NH2-SASAPMVSGVAALVLE.


CONCLUSIONS
A novel extracellular alkaline serine protease was isolated from S. maltophilia strain S-1. The optimal pH of the proteolytic activity was pH 12.0.


CONCLUSIONS
The extremely high optimal pH and heat stability of the alkaline serine protease SmP-1 might make it widely applicable to food and other industries.
Miyaji
T
T
Department of Food Science and Technology, Faculty of Bioindustry, Tokyo University of Agriculture, Abashiri, Hokkaido, Japan. t-miyaji@bioindustry.nodai.ac.jp
Otta
Y
Y
Shibata
T
T
Mitsui
K
K
Nakagawa
T
T
Watanabe
T
T
Niimura
Y
Y
Tomizuka
N
N
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification; D010450:Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification; D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010802:Phylogeny; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification; D012988:Soil Microbiology; D020615:Stenotrophomonas maltophilia / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification; D013696:Temperature
D001426:Bacterial Proteins; D010450:Endopeptidases; D012697:Serine Endopeptidases; C087822:alkaline protease