Characterization of Oceanobacillus Alkaliphilic Protease Expressed in Brevibacillus choshinensis

Abstract

Alkaliphilic and extremely halo-tolerant bacterium, Oceanobacillus iheyensis HTE831, isolated from deep-sea sediment at a depth of 1050 m by Lu et al. ［FEMS Microbiol. Lett., 205, 291-297 （2001）］ encodes subtilisin-like protease gene（OB2598）. This O. iheyensis subtilisin-like protease（OihS）was expressed in a Brevibacillus choshinensis expression-secretion system, partially purified, and then characterized. B. choshinensis cells harboring expression vector pBIC2-OihS-His, encoding signal sequence of Brevibacillus cell wall protein-pro-OihS-His-tag protein, secreted the OihS as a pro-form to the culture medium. Subsequently, this pro-form was observed to have been processed to mature form in the culture medium. Partially purified OihS protein showed the highest proteolytic activity at 60 ℃ and pH 10-11. The proteolytic activity and stability were enhanced by the addition of Ca^＋＋ ions. The primary sequence homology and its heat-stability suggested that OihS belongs to the thermostable and alkaliphilic thermitase-family of subtilases.