Purification and characterization of a novel extracellular lipase catalyzing hydrolysis of oleyl benzoate from Acinetobacter nov sp strain KM109

A new lipase (OBase) which efficiently hydrolyzes oleyl benzoate (OB) was f ound in the culture supernatant of Acinetobacter nov, sp. strain KM109, a n ew isolate growing in a minimum medium containing on as the sole carbon sou rce. OBase was purified to homogeneity with 213-fold purification and 0.8% yield. The molecular weight was estimated to be 62,000 +/- 1,000 by SDS-PAG E under denatured-reduced conditions and to be 50,000 +/- 1,000 by gel-filt ration HPLC under native conditions; these findings indicate that OBase is a monomeric enzyme. The optimum temperature and pH of OBase were about 45 d egrees C and pH 8. Temperature and pH stabilities were at or lower than 35 degrees C and in a range of pH 6-8, respectively. Purified OBase preferenti ally hydrolyzed p-nitrophenyl benzoate (pNPB) over p-nitrophenyl acetate (p NPA) or p-nitrophenyl caproate (pNPC) [pNPB/pNPA=20 and pNPB/pNPC=5.4], ind icating that OBase has a high affinity for benzoyl esters. Partial amino-ac id sequences of OBase fragments obtained after lysyl endopeptidase treatmen t showed no similarity with known proteins.