First co-expression of a lipase and its specific foldase obtained by metagenomics.

BACKGROUND: Metagenomics is a useful tool in the search for new lipases that might have characteristics that make them suitable for application in biocatalysis. This paper reports the cloning, co-expression, purification and characterization of a new lipase, denominated LipG9, and its specific foldase, LifG9, from a metagenomic library derived from a fat-contaminated soil. RESULTS: Within the metagenomic library, the gene lipg9 was cloned jointly with the gene of the foldase, lifg9. LipG9 and LifG9 have 96% and 84% identity, respectively, with the corresponding proteins of Aeromonas veronii B565. LipG9 and LifG9 were co-expressed, both in N-truncated form, in Escherichia coli BL21(DE3), using the vectors pET28a(+) and pT7-7, respectively, and then purified by affinity chromatography using a Ni(2+) column (HiTrap Chelating HP). The purified enzyme eluted from the column complexed with its foldase. The molecular masses of the N-truncated proteins were 32 kDa for LipG9, including the N-terminal His-tag with 6 residues, and 23 kDa for LifG9, which did not have a His-tag. The biochemical and kinetic characteristics of the purified lipase-foldase preparation were investigated. This preparation was active and stable over a wide range of pH values (6.5-9.5) and temperatures (10-40°C), with the highest specific activity, of 1500 U mg(-1), being obtained at pH 7.5 at 30°C. It also had high specific activities against tributyrin, tricaprylin and triolein, with values of 1852, 1566 and 817 U mg(-1), respectively. A phylogenetic analysis placed LipG9 in the lipase subfamily I.1. A comparison of the sequence of LipG9 with those of other bacterial lipases in the Protein Data Bank showed that LipG9 contains not only the classic catalytic triad (Ser(103), Asp(250), His(272)), with the catalytic Ser occurring within a conserved pentapeptide, Gly-His-Ser-His-Gly, but also a conserved disulfide bridge and a conserved calcium binding site. The homology-modeled structure presents a canonical α/ß hydrolase folding type I. CONCLUSIONS: This paper is the first to report the successful co-expression of a lipase and its associated foldase from a metagenomic library. The high activity and stability of Lip-LifG9 suggest that it has a good potential for use in biocatalysis.

Structure of glyceraldehyde-3-phosphate dehydrogenase from Paracoccidioides lutzii in complex with an aldonic sugar acid.

The pathogen Paracoccidioides lutzii (Pb01) is found in South America countries Colombia, Ecuador, Venezuela and Brazil, especially in the central, west, and north regions of the latter. It belongs to the Ajellomycetaceae family, Onygenales order, and is typically thermodimorphic, presenting yeast cells when it grows in animal tissues, but mycelia when in the environment, where it produces the infectious propagule. This fungus is one of the etiologic agents of Paracoccidioidomycosis (PCM), the most important endemic fungal infection in Latin America. Investigations on its genome have contributed to a better understanding about its metabolism and revealed the complexity of several metabolic glycolytic pathways. Glyceraldehyde-3-Phosphate Dehydrogenase from Paracoccidioides lutzii (PlGAPDH) is considered a moonlighting protein and participates in several biological processes of this pathogen. The enzyme was expressed and purified, as seen in SDS-PAGE gel, crystallized and had its three dimensional structure (3D) determined in complex with NAD+, a sulphate ion and d-galactonic acid, therefore, a type of 'GAA site'. It is the first GAPDH structure to show this chemical type in this site and how this protein can bind an acid derived from oxidation of a linear hexose.

Structure solution and analyses of the first true lipase obtained from metagenomics indicate potential for increased thermostability.

Metagenomics is a modern approach to discovery of new enzymes with novel properties. This article reports the structure of a new lipase, belonging to family I.1, obtained by means of metagenomics. Its structure presents a fold typical of α/ß hydrolases, with the lid in closed conformation. The protein was previously shown to present high thermostability and to be stable in aqueous solutions of polar organic solvents at high concentrations [30% (V/V)]. Molecular dynamics studies showed that the protein maintains its structure well in organic solvents. They also suggested that its thermostability might be enhanced if it were mutated to present a disulfide bond similar to that typically found in lipase family I.2. These findings identify this lipase as a good candidate for further improvement through protein engineering.

Biochemical characterization and application of a new lipase and its cognate foldase obtained from a metagenomic library derived from fat-contaminated soil.

LipMF3 is a new lipase isolated from a metagenomic library derived from a fat-contaminated soil. It belongs to the lipase subfamily I.1 and has identities of 68% and 67% with lipases of Chromobacterium violaceum and C. amazonense, respectively. Genes encoding LipMF3 and its cognate foldase, LifMF3, were cloned and co-expressed in Escherichia coli. The highest hydrolytic activity of purified Lip-LifMF3 was at 40 °C and pH 6.5. Under these conditions, the highest activity was against tributyrin (1650 U mg-1), but it also had high activity against olive oil (862 U mg-1). It was stable in hydrophilic organic solvents (25%, v/v in water) with residual activity around 100% after 24 h. It also showed stability over a wide pH range (5.5 to 11) with residual activity above 80% after 24 h. Lip-LifMF3 was immobilized by covalent bonding onto Immobead 150P and by adsorption onto Sepabeads FP-BU. The latter preparation gave the best results, producing 94% conversion after 5 h for the synthesis of ethyl oleate and a 90% enantiomeric excess of the product (R)­1­phenylethyl acetate for the kinetic resolution of (R,S)­1­phenyl­1­ethanol. The results obtained in this work provide a basis for the development of applications of Lip-LifMF3 in biocatalysis.

Immobilization and characterization of a new regioselective and enantioselective lipase obtained from a metagenomic library.

In previous work, a new lipase and its cognate foldase were identified and isolated from a metagenomic library constructed from soil samples contaminated with fat. This new lipase, called LipG9, is a true lipase that shows specific activities that are comparable to those of well-known industrially-used lipases with high activity against long-chain triglycerides. In the present work, LipG9 was co-expressed and co-immobilized with its foldase, on an inert hydrophobic support (Accurel MP1000). We studied the performance of this immobilized LipG9 (Im-LipG9) in organic media, in order to evaluate its potential for use in biocatalysis. Im-LipG9 showed good stability, maintaining a residual activity of more than 70% at 50 °C after incubation in n-heptane (log P 4.0) for 8 h. It was also stable in polar organic solvents such as ethanol (log P -0.23) and acetone (log P -0.31), maintaining more than 80% of its original activity after 8 h incubation at 30 °C. The synthesis of ethyl esters was tested with fatty acids of different chain lengths in n-heptane at 30 °C. The best conversions (90% in 3 h) were obtained for medium and long chain saturated fatty acids (C8, C14 and C16), with the maximum specific activity, 29 U per gram of immobilized preparation, being obtained with palmitic acid (C16). Im-LipG9 was sn-1,3-specific. In the transesterification of the alcohol (R,S)-1-phenylethanol with vinyl acetate and the hydrolysis of the analogous ester, (R,S)-1-phenylethyl acetate, Im-LipG9 showed excellent enantioselectivity for the R-isomer of both substrates (E> 200), giving an enantiomeric excess (ee) of higher than 95% for the products at 49% conversion. The results obtained in this work provide the basis for the development of applications of LipG9 in biocatalysis.