Biochemical and molecular characterization of Staphylococcus simulans lipase

Staphylococcus simulans strain secretes a non-induced lipase in the culture medium. Staphylococcus simulans lipase (SSL), purified to homogeneity, is a tetrameric protein (160 kDa) corresponding to the association of four lip ase molecules. The 30 N-terminal amino acid residues were sequenced. This s equence is identical to the one of Staphylococcus aureus PS54 lipase (SAL P S54) and exhibits a high degree of homology with Staphylococcus aureus NCTC 8530 lipase (SAL NCTC8530), Staphylococcus hyicus lipase (SHL) and Staphylo coccus epidermis RP62A lipase (SEL RP62A) sequences. But the cloning and se quencing of the part of the gene encoding the mature lipase show some diffe rences from SAL PS54 sequence, which suggest that it is a new sequence. The lipase activity was maximal at pH 8.5 and 37 degreesC. SSL is able to hydr olyze triacylglycerols without chain length specificity. A specific activit y of about 1000 U/mg was measured on tributyrin or triolein as substrate at 37 OC and at pH 8.5 in the presence of 3 rum CaCl2 In contrast to other st aphylococcal lipases previously characterized, Ce2+ is not required to expr ess the activity of SSL. SSL was found to be stable between pH 4 and pH 9. The enzyme is inactivated after a few minutes when incubated at 60 degreesC . Using tripropionin as substrate, SSL does not present the interfacial act ivation phenomenon. In contrast to many lipases, SSL is able to hydrolyze i ts substrate in the presence of bile salts or amphiphilic proteins. (C) 200 1 Societe francaise de biochimie et biologie moleculaire / Editions scienti fiques et medicales Elsevier SAS. All rights reserved.