Recombinant phospholipase A sub(1) of the outer membrane of psychrotrophic Yersinia pseudotuberculosis: Expression, purification, and characterization

The pldA gene encoding membrane-bound phospholipase A sub(1) of Yersinia pseudotuberculosis was cloned and expressed in Escherichia coli cells. Recombinant phospholipase A sub(1) (rPldA) was isolated from inclusion bodies dissolved in 8 M urea by two-stage chromatography (ion-exchange and gel-filtration chromatography) as an inactive monomer. The molecular mass of the rPldA determined by MALDI-TOF MS was 31.7 plus or minus 0.4 kDa. The highly purified rPldA was refolded by 10-fold dilution with buffer containing 10 mM Triton X-100 and subsequent incubation at room temperature for 16 h. The refolded rPldA hydrolyzed 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine in the presence of calcium ions. The enzyme exhibited maximal activity at 37 degree C and nearly 40% of maximal activity at 15 degree C. The phospholipase A sub(1) was active over a wide range of pH from 4 to 11, exhibiting maximal activity at pH 10. Spatial structure models of the monomer and the dimer of Y. pseudotuberculosis phospholipase A sub(1) were constructed, and functionally important amino acid residues of the enzyme were determined. Structural differences between phospholipases A sub(1) from Y. pseudotuberculosis and E. coli, which can affect the functional activity of the enzyme, were revealed.