Bacterial biocatalysts: molecular biology, three-dimensional structures, and biotechnological applications of lipases.
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.
Jaeger
K E
KE
Lehrstuhl Biologie der Mikroorganismen, Ruhr-Universität, Bochum, Germany. karl-erich.jaeger@ruhr-uni-bochum.de
Dijkstra
B W
BW
Reetz
M T
MT
D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D001709:Biotechnology; D002384:Catalysis; D015964:Gene Expression Regulation, Bacterial; D008049:Lipase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D011487:Protein Conformation; D017510:Protein Folding
D008049:Lipase