Expression and characterization of Ca2+-independent lipase from Bacillus pumilus B26

A lipase-producing Bacillus pumilus strain (B26) was isolated from a soil sample collected in Korea. The cloned gene showed that the lipase B26 composed of a 34-amino-acid signal sequence and a 181-amino-acid mature part corresponding to a molecular mass (M_r) of 19,225. Based on the M_r and the protein sequence, the lipase B26 belongs to the lipase family I.4. The optimum temperature and pH of the purified enzyme were 35 °C and 8.5, respectively. The lipase B26 showed a ‘Ca²⁺-independent thermostability and catalytic activity’. These are novel properties observed for the first time in lipase B26 among all bacterial lipases and correspond with the suggestion that this enzyme had no Ca²⁺-binding motif around the catalytic His156 residue. This enzyme seems to be a true lipase based on the experimental results that it could hydrolyze various long-chain triglycerides (C₁₄–C₁₈) and triolein (C_18:1) and that it showed a typical interfacial activation mechanism toward both tripropionin and p-nitrophenyl butyrate.