Preliminary characterisation of a lipolytic activity from an extremely halophilic archaeon, Natronococcus sp.

A crude preparation obtained from an extremely halophilic archaeon, Natronococcus sp. strain TC6, hydrolysed olive oil, indicating the presence of a true lipase. This preparation was partially characterised using p-nitrophenyl palmitate (pNPP). It hydrolysed pNPP optimally at 4 M NaCl, with no activity in the absence of salt. With 4 M NaCl, activity was maximal at 50 °C and pH 7. The activity was highly thermostable, with more than 90% of original activity being retained when incubated for 60 min at 50 °C. Salt affected the thermostability. The residual pNPP-hydrolysing activity fell to 50% in 76 min when incubated at 80 °C with 4 M NaCl, and in 35 min when incubated without NaCl. The preparation preferentially hydrolysed pNP-esters of long-chain fatty acids (C10–C18), having maximum activity on pNPP (C16). The activity was inhibited by PMSF, indicating the presence of a serine residue in the active site. These results strongly suggest the presence of a true lipase and therefore, this archaeon deserves further attention, since true lipases have not previously been reported in the archaea.