Purification and properties of a protease produced by Bacillus subtilis CN2 isolated from a Vietnamese fish sauce

Bacillus subtilis CN2 isolated from a Vietnamese fish sauce produced a large quantity of an alkaline protease, when grown on a soy peptone medium. The protease was purified to an electrophoretically homogeneous state and crystallized in its pure condensed solution. The molecular weight was determined to be 27,636 Da, and the N-terminal amino acid sequence was AQSVPYGISQIKAPAL. The optimum pH and temperature were pH 10.0 and 50 degreesC, respectively. The protease was active over a wide pH range of pH 7.0-11.0, and also active over a broad temperature range of 30-60 degreesC. The enzyme was potently inhibited by 1 mM phenylmethanesulphonyl fluoride, but resistant to 1 mM sodium dodecyl sulphate (SDS).