A Halophilic Serine Proteinase from Halobacillus sp. SR5-3 Isolated from Fish Sauce: Purification and Characterization

Abstract

A halophilic bacterium was isolated from fish sauce, classified, and named Halobacillus sp. SR5-3. A purified 43-kDa proteinase produced by this bacterium showed optimal activity at 50 °C and pH 9–10 in 20% NaCl. The activity of the enzyme was enhanced about 2.5-fold by the addition of 20–35% NaCl, and the enzyme was highly stabilized by NaCl. It was found to be a serine proteinase related to either chymotrypsin or subtilisin. It absolutely preferred Ile at the P₂ position of substrates. Thus, the enzyme was found to be a halophilic serine proteinase with unique substrate specificity.

• moderately halophilic bacteria
• Halobacillus sp.
• serine proteinase
• fish sauce
• fluorescence resonance energy transfer substrate (FRETS)