Engineering catalytic efficiency of thermophilic lipase from <i>Geobacillus zalihae</i> by hydrophobic residue mutation near the catalytic pocket

Abstract

In-silico and experimental investigations were conducted to explore the effects of substituting hydrophobic residues; Val, Met, Leu, Ile, Trp and Phe into the oxyanion Q114 of T1 lipase. We hypothesized that the oxyanion Q114, involved in substrate binding is also associated with modulation of conformational stability and in conferring specific enzyme attributes. The insilico investigations accurately predicted the quality of the protein packing in some of the variants. Our study found by altering the hydrophobicity of the oxyanion 114, remarkably altered enzyme conformational stability and catalytic attributes. Substitution with Leu resulted improvements in four out of the six tested characteristics. The hydrophobic Leu might have improved local structure folding and increased hydrophobic interactions with other residues in the vicinity of the mutation. The Met variant showed higher activity over the wild-type in hydrolyzing a wider range of natural oils. The bulky amino acids, Phe and Trp negatively affected T1 lipase and resulted in the largest disruption of protein stability and inferior enzyme characteristics. We have successfully illustrated that a single point residue changes at oxyanion 114 could result in a myriad of enzyme attributes, which implied there was some interplay between hydrophobicity and conformation for lipase catalytic functions.