Biochemical and molecular characterisation of a thermoactive, alkaline and detergent-stable lipase from a newly isolated Staphylococcus aureus strain

A newly soil-isolated Staphylococcus aureus strain secretes a non-induced lipase in the culture medium. The extracellular lipase from S. aureus (SAL3) is purified to homogeneity. The purified enzyme is a tetrameric protein (180 kDa) corresponding to the association of four lipase molecules. The 15 N-terminal amino acid residues showed a high degree of homology with other staphylococcal lipase sequences. The part of the gene encoding the mature SAL3 is cloned and sequenced. The deduced polypeptide sequence, corresponding to the mature SAL3, was very similar to the mature Staphylococcus simulans lipase sequence with two additional amino acid residues (LK) at the N-terminus of SAL3. The lipase activity is maximal at pH 9.5 and 55 °C. The specific activity of about 4200 U/mg or 3500 U/mg was measured using tributyrin or olive oil emulsion as substrate, respectively, at pH 9.5 and 55 °C.In contrast to other staphylococcal lipases previously characterised, SAL3 is found to be stable between pH 5 and 12 after 24 h incubation. The enzyme retained 50% of its activity after 60 min incubation at 60 °C. This novel lipase is able to hydrolyse its substrate in presence of various oxidizing agents as well as some surfactants and some commercial detergents, then SAL3 can be considered as a good candidate for industrial and biotechnological applications.