Identification and Biochemical Characterization of a Novel Hormone-Sensitive Lipase Family Esterase Est19 from the Antarctic Bacterium Pseudomonas sp. E2-15

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 Ser(155), Asp(253), and His(282) residues. The catalytic efficiency (k(cat)/K-m) of Est19 for the pNPC6 substrate is 148.68 s(-1)mM(-1) at 40 & DEG;C. Replacing Glu(154) juxtaposed to the critical catalytic serine with Asp (E154 & RARR;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 & DEG;C, while ~50% of its activity was retained at 0 & DEG;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.

Automated summary

Est19 is a novel hormone-sensitive lipase (HSL) family esterase with a conserved catalytic triad structure, exhibiting high catalytic efficiency towards the substrate pNPC6. Mutation experiment showed that replacing the adjacent glutamic acid to the critical catalytic serine significantly reduces the activity and efficiency of the enzyme.