A novel cold-adapted phospholipase A1 from Serratia sp. xjF1: Gene cloning, expression and characterization

The gene encoding a cold-adapted phospholipase A1 (PLA1) from a psychrotrophic, glacier soil bacterium Serratia sp. xjF1 was cloned by two-step PCR (general PCR and TAIL-PCR). The full-length fragment comprised two open reading frames plA and plS. The gene product of plA encoding 320 amino acids with a molecular weight of 33.8 kDa was identified as a phospholipase A1. Its amino acid sequence exhibited the highest homology to PLA1 of Serratia marcescens (71%). plS encoded a protein of 251 amino acids, which showed no enzymatic activity. The result of plA expression in Escherichia coli indicated that plS might improve the efficient expression of PLA1 in E. coli. Furthermore, PLA1 was functionally expressed in Pichia pastoris, yielding 41.8 U/mL in a 3.7 L fermentor. The purified recombinant phospholipase A1 (rPLA1) had features typical of cold-adapted enzymes with a temperature optimum of 35 °C and a maximum activity of 70% at 10 °C. The rate of catalysis was optimal at pH 9.0 and the enzyme could be slightly activated by Ca2+. This is the first report on gene isolation and expression of cold-adapted PLA1.