Bacterial Biocatalysts: Molecular Biology, Three-Dimensional Structures, and Biotechnological Applications of Lipases

Abstract

Bacteria produce and secrete lipases, which can catalyze both the hydrolysis and the synthesis of long-chain acylglycerols. These reactions usually proceed with high regioselectivity and enantioselectivity, and, therefore, lipases have become very important stereoselective biocatalysts used in organic chemistry. High-level production of these biocatalysts requires the understanding of the mechanisms underlying gene expression, folding, and secretion. Transcription of lipase genes may be regulated by quorum sensing and two-component systems; secretion can proceed either via the Sec-dependent general secretory pathway or via ABC transporters. In addition, some lipases need folding catalysts such as the lipase-specific foldases and disulfide-bond-forming proteins to achieve a secretion-competent conformation. Three-dimensional structures of bacterial lipases were solved to understand the catalytic mechanism of lipase reactions. Structural characteristics include an alpha/beta hydrolase fold, a catalytic triad consisting of a nucleophilic serine located in a highly conserved Gly-X-Ser-X-Gly pentapeptide, and an aspartate or glutamate residue that is hydrogen bonded to a histidine. Four substrate binding pockets were identified for triglycerides: an oxyanion hole and three pockets accommodating the fatty acids bound at position sn-1, sn-2, and sn-3. The differences in size and the hydrophilicity/hydrophobicity of these pockets determine the enantiopreference of a lipase. The understanding of structure-function relationships will enable researchers to tailor new lipases for biotechnological applications. At the same time, directed evolution in combination with appropriate screening systems will be used extensively as a novel approach to develop lipases with high stability and enantioselectivity.

Effect of Environmental and Nutritional Parameters on the Extracellular Lipase Production by <i>Aspergillus niger</i>

“…Microorganisms produced by Lipase have been found in various occupant such as industrial wastes, oilseeds, soil contaminated with oil, vegetable oil processing factories, dairies product and decaying food [17], coal crest and compost blend [18]. Lipase-producing microorganisms include actinomyces, fungi, yeasts, and bacteria.…”

Molecular cloning, over expression and characterization of thermoalkalophilic esterases isolated from Geobacillus sp.

“…They are widely distributed in animals, plants and microorganisms (Bornscheuer 2002). These enzymes are of special interest in a variety of biotechnological applications because of their many useful properties such as broad range of natural and non-natural substrates, require no cofactor in the reactions, stability in organic solvents and exhibiting high regio and stereoselectivity (Faber 1997;Guagliardi et al 1989;Jaeger et al 1999). Every year novel biotechnological applications are established using esterases because of their important industrial and medical roles in the synthesis and hydrolysis of stereospecific compounds, including the metabolic processing of drugs and antimicrobial agents (Bornemann et al 1992;Margolin 1993;Moher et al 1989;Quax and Broekhuizen 1994).…”

A feruloyl esterase derived from a leachate metagenome library

“…The deduced amino acid sequence of Fae6 contained a -G-E-S-A-G-sequence (position 217-221), which corresponds well with the pentapeptide -G-x-S-x-G-signature motif that is generally conserved in many esterolytic enzymes (5,24). Multiple sequence alignment of Fae6 with a recently published metagemomic derived esterase (25) from family VII and the other related sequence from the BLASTp hits showed that the following residues were highly conserved: Ser253 within the G-E-S-A-G sequence motif, as well as the C-terminus located Glu307 and His507 ( Fig.…”