Liu_2021_Biomolecules_11_1552

Esterases represent an important class of enzymes with a wide variety of industrial applications. A novel hormone-sensitive lipase (HSL) family esterase, Est19, from the Antarctic bacterium Pseudomonas sp. E2-15 is identified, cloned, and expressed. The enzyme possesses a GESAG motif containing an active serine (S) located within a highly conserved catalytic triad of Ser155, Asp253, and His282 residues. The catalytic efficiency (kcat/Km) of Est19 for the pNPC6 substrate is 148.68 s-1 mM-1 at 40 C. Replacing Glu154 juxtaposed to the critical catalytic serine with Asp (E154->D substitution) reduced the -activity and catalytic efficiency of the enzyme two-fold, with little change in the substrate affinity. The wild-type enzyme retained near complete activity over a temperature range of 10-60 C, while ~50% of its activity was retained at 0 C. A phylogenetic analysis suggested that Est19 and its homologs may represent a new subfamily of HSL. The thermal stability and stereo-specificity suggest that the Est19 esterase may be useful for cold and chiral catalyses.