Novel thermophilic and thermostable lipolytic enzymes from a Thailand hot spring metagenomic library

Abstract

Functional screening for lipolytic enzymes from a metagenomic library (origin: Jae Sawn hot spring, Thailand) resulted in isolation of a novel patatin-like phospholipase (PLP) and an esterase (Est1). PLP contained four conserved domains similar to other patatin-like proteins with lipid acyl hydrolase activity. Likewise, sequence alignment analysis revealed that Est1 can be classified as a family V bacterial lipolytic enzyme. Both PLP and Est1 were expressed heterologously as soluble proteins in E. coli and exhibited more than 50% of their maximal activities at alkaline pH, of 7–9 and 8–10, respectively. In addition, both enzymes retained more than 50% of maximal activity in the temperature range of 50–75 °C, with optimal activity at 70 °C and were stable at 70 °C for at least 120 min. Both PLP and Est1 exhibited high V max toward p-nitrophenyl butyrate. The enzymes had activity toward both short-chain (C 4 and C 5) and long chain (C 14 and C 16) fatty acid esters. The isolated enzymes, are therefore, different from other known patatin-like phospholipases and esterases, which usually show no activity for substrates longer than C 10. We suggest that PLP and EstA enzymes are novel and have a; b potential use in industrial applications.