Characterization of a Novel Esterase Belonging to Family V from Marinobacter flavimaris

Lipolytic enzymes have attracted enormous attentions because of their ability in ester hydrolysis, ester synthesis, transesterification and other biochemical reactions. Bacteria are important sources of lipolytic enzymes applied in industry. Here, a novel lipolytic enzyme encoded by esterase gene est1347 was identified in Marinobacter flavimaris WLL162, and was purified and characterized. The lipolytic enzyme Est1347 consisted of 312 amino acid residues and a 21-amino-acids N-terminal signal peptide with a predicted molecular weight of 34.2 kDa. It belongs to family V of bacterial lipolytic enzymes based on the amino acid sequence homology analysis. Est1347 is a mesophilic and alkali-resistant enzyme with the highest activity at 45 degrees C and pH 8.5; it is stable at temperatures below 50 degrees C and pH 7.5 - 11.0. Est1347 showed a preference for middle-length chain substrate p-NPC10 and a wide range of other substrates. The K-m , V-max , K-cat and K-cat/K-m values of Est1347 for p-NPC10 in pH 8.5 at 45 degrees C were 0.9411 mmol L-1 , 1285 mu mol min(-1) mg(-1) , 698.91 s(-1) and 743.65 s(-1) (mmol L-1)(-1) , respectively. It is also tolerant to the metal ions, organic solvents and detergents. In conclusion, the esterase Est1347 laid a foundation for further study of bacterial lipolytic enzyme family V.