Characterization, crystallization and preliminary X‐ray diffraction analysis of an ( S )‐specific esterase ( pf EstA) from Pseudomonas fluorescens KCTC 1767: enantioselectivity for potential industrial applications

The structures and reaction mechanisms of enantioselective hydrolases, which can be used in industrial applications such as biotransformations, are largely unknown. Here, the X‐ray crystallographic study of a novel ( S )‐specific esterase ( pf EstA) from Pseudomonas fluorescens KCTC 1767, which can be used in the production of ( S )‐ketoprofen, is described. Multiple sequence alignments with other hydrolases revealed that pf EstA contains a conserved Ser67 within the S‐ X ‐ X ‐K motif as well as a highly conserved Tyr156. Recombinant protein containing an N‐terminal His tag was expressed in Escherichia coli , purified to homogeneity and characterized using SDS–PAGE, MALDI‐TOF MS and enantioselective analysis. pf EstA was crystallized using a solution consisting of 1  M sodium citrate, 0.1  M CHES pH 9.5, and X‐ray diffraction data were collected to a resolution of 1.9 Å with an R merge of 7.9%. The crystals of pf EstA belonged to space group P 2 1 2 1 2 1 , with unit‐cell parameters a = 65.31, b = 82.13, c  = 100.41 Å, α = β = γ = 90°.