The utilization of cold active lipases in organic solvents proves an excellent approach for chiral synthesis and modification of fats and oil due to the inherent flexibility of lipases under low water conditions. In order to verify whether this lipase can function as a valuable synthetic catalyst, the mechanism concerning activation of the lid and interacting solvent residues in the presence of organic solvent must be well understood. A new alkaline cold-adapted lipase, AMS8, from Pseudomonas fluorescens was studied for its structural adaptation and flexibility prior to its exposure to non-polar, polar aprotic and protic solvents. Solvents such as ethanol, toluene, DMSO and 2-propanol showed to have good interactions with active sites. Asparagine (Asn) and tyrosine (Tyr) were key residues attracted to solvents because they could form hydrogen bonds. Unlike in other solvents, Phe-18, Tyr-236 and Tyr-318 were predicted to have aromatic-aromatic side-chain interactions with toluene. Non-polar solvent also was found to possess highest energy binding compared to polar solvents. Due to this circumstance, the interaction of toluene and AMS8 lipase was primarily based on hydrophobicity and molecular recognition. The molecular dynamic simulation showed that lid 2 (residues 148-167) was very flexible in toluene and Ca(2+). As a result, lid 2 moves away from the catalytic areas, leaving an opening for better substrate accessibility which promotes protein activation. Only a single lid (lid 2) showed the movement following interactions with toluene, although AMS8 lipase displayed double lids. The secondary conformation of AMS8 lipase that was affected by toluene observed a reduction of helical strands and increased coil structure. Overall, this work shows that cold active lipase, AMS8 exhibits distinguish interfacial activation and stability in the presence of polar and non-polar solvents.
Photobacterium species are Gram-negative coccobacilli which are distributed in marine habitats worldwide. Some species are unique because of their capability to produce luminescence. Taxonomically, about 23 species and 2 subspecies are validated to date. Genomes from a few Photobacterium spp. have been sequenced and studied. They are considered a special group of bacteria because some species are capable of producing essential polyunsaturated fatty acids, antibacterial compounds, lipases, esterases and asparaginases. They are also used as biosensors in food and environmental monitoring and detectors of drown victim, as well as an important symbiont.
The use of T1 lipase in automatic dishwashing detergent (ADD) is well established, but efficiency in hard water is very low. A new enzymatic environmentally-friendly dishwashing was formulated to be efficient in both soft and hard water. Thermostable enzymes such as T1 lipase from Geobacillus strain T1, Rand protease from Bacillussubtilis strain Rand, and Maltogenic amylase from Geobacillus sp. SK70 were produced and evaluated for an automatic dishwashing detergent formulation. The components of the new ADD were optimized for compatibility with these three enzymes. In compatibility tests of the enzymes with different components, several criteria were considered. The enzymes were mostly stable in non-ionic surfactants, especially polyhydric alcohols, Glucopon UP 600, and in a mixture of sodium carbonate and glycine (30:70) buffer at a pH of 9.25. Sodium polyacrylate and sodium citrate were used in the ADD formulation as a dispersing agent and a builder, respectively. Dishwashing performance of the formulated ADDs was evaluated in terms of percent of soil removed using the Leenert's Improved Detergency Tester. The results showed that the combination of different hydrolysis enzymes could improve the washing efficiency of formulated ADD compared to the commercial ADD "Finish" at 40 and 50 C.
Less sedimentation and convection in a microgravity environment has become a well-suited condition for growing high quality protein crystals. Thermostable T1 lipase derived from bacterium Geobacilluszalihae has been crystallized using the counter diffusion method under space and earth conditions. Preliminary study using YASARA molecular modeling structure program for both structures showed differences in number of hydrogen bond, ionic interaction, and conformation. The space-grown crystal structure contains more hydrogen bonds as compared with the earth-grown crystal structure. A molecular dynamics simulation study was used to provide insight on the fluctuations and conformational changes of both T1 lipase structures. The analysis of root mean square deviation (RMSD), radius of gyration, and root mean square fluctuation (RMSF) showed that space-grown structure is more stable than the earth-grown structure. Space-structure also showed more hydrogen bonds and ion interactions compared to the earth-grown structure. Further analysis also revealed that the space-grown structure has long-lived interactions, hence it is considered as the more stable structure. This study provides the conformational dynamics of T1 lipase crystal structure grown in space and earth condition.
A total of 97 amino acids, considered as the signal peptide and transmembrane segments were removed from 205y lipase gene using polymerase chain reaction technique that abolished the low activity of this enzyme. The mature enzyme was expressed in Escherichia coli using pBAD expression vector, which gave up to a 13-fold increase in lipase activity. The mature 205y lipase (without signal peptide and transmembrane; -SP/TM) was purified to homogeneity using the isoelectric focusing technique with 53% recovery. Removing of the signal peptide and transmembrane segments had resulted in the shift of optimal pH, an increase in optimal temperature and tolerance towards more water-miscible organic solvents as compared to the characteristics of open reading frame (ORF) of 205y lipase. Also, in the presence of 1mM inhibitors, less decrease in the activity of mature 205y lipase was observed compared to the ORF of the enzyme. Protein structure modeling showed that 205y lipase consisted of an α/β hydrolase fold without lid domain. However, the transmembrane segment could effect on the enzyme activity by covering the active site or aggregation the protein.
Background:Pseudomonas protein expression in E. coli is known to be a setback due to significant genetic variation and absence of several genetic elements in E. coli for regulation and activation of Pseudomonas proteins. Modifications in promoter/repressor system and shuttle plasmid maintenance have made the expression of stable and active Pseudomonas protein possible in both Pseudomonas sp. and E. coli. Objectives: Construction of shuttle expression vectors for regulation and overexpression of Pseudomonas proteins in Pseudomonas sp. and E. coli. Materials and Methods:Pseudomonas-Escherichia shuttle expression vectors, pCon2(3), pCon2(3)-Kan and pCon2(3)-Zeo as well as E. coli expression vectors of pCon4 and pCon5 were constructed from pUCP19-, pSS213-, pSTBlue-1- and pPICZαA-based vectors. Protein overexpression was measured using elastase strain K as passenger enzyme in elastinolytic activity assay. Results: The integration of two series of IPTG inducible expression cassettes in pCon2(3), pCon2(3)-Kan and pCon2(3)-Zeo, each carrying an E. coli lac-operon based promoter, Plac, and a tightly regulated T7(A1/O4/O3) promoter/repressor system was performed to facilitate overexpression study of the organic solvent-tolerant elastase strain K. These constructs have demonstrated an elastinolytic fold of as high as 1464.4 % in comparison to other published constructs. pCon4 and pCon5, on the other hand, are series of pCon2(3)-derived vectors harboring expression cassettes controlled by PT7(A1/O4/O3) promoter, which conferred tight regulation and repression of basal expression due to existence of respective double operator sites, O3 and O4, and lacIq. Conclusions: The constructs offered remarkable assistance for overexpression of heterogeneous genes in Pseudomonas sp. and E. coli for downstream applications such as in industries and structural biology study.
The dynamics and conformational landscape of proteins in organic solvents are events of potential interest in nonaqueous process catalysis. Conformational changes, folding transitions, and stability often correspond to structural rearrangements that alter contacts between solvent molecules and amino acid residues. However, in nonaqueous enzymology, organic solvents limit stability and further application of proteins. In the present study, molecular dynamics (MD) of a thermostable Geobacillus zalihae T1 lipase was performed in different chain length polar organic solvents (methanol, ethanol, propanol, butanol, and pentanol) and water mixture systems to a concentration of 50%. On the basis of the MD results, the structural deviations of the backbone atoms elucidated the dynamic effects of water/organic solvent mixtures on the equilibrium state of the protein simulations in decreasing solvent polarity. The results show that the solvent mixture gives rise to deviations in enzyme structure from the native one simulated in water. The drop in the flexibility in H2O, MtOH, EtOH and PrOH simulation mixtures shows that greater motions of residues were influenced in BtOH and PtOH simulation mixtures. Comparing the root mean square fluctuations value with the accessible solvent area (SASA) for every residue showed an almost correspondingly high SASA value of residues to high flexibility and low SASA value to low flexibility. The study further revealed that the organic solvents influenced the formation of more hydrogen bonds in MtOH, EtOH and PrOH and thus, it is assumed that increased intraprotein hydrogen bonding is ultimately correlated to the stability of the protein. However, the solvent accessibility analysis showed that in all solvent systems, hydrophobic residues were exposed and polar residues tended to be buried away from the solvent. Distance variation of the tetrahedral intermediate packing of the active pocket was not conserved in organic solvent systems, which could lead to weaknesses in the catalytic H-bond network and most likely a drop in catalytic activity. The conformational variation of the lid domain caused by the solvent molecules influenced its gradual opening. Formation of additional hydrogen bonds and hydrophobic interactions indicates that the contribution of the cooperative network of interactions could retain the stability of the protein in some solvent systems. Time-correlated atomic motions were used to characterize the correlations between the motions of the atoms from atomic coordinates. The resulting cross-correlation map revealed that the organic solvent mixtures performed functional, concerted, correlated motions in regions of residues of the lid domain to other residues. These observations suggest that varying lengths of polar organic solvents play a significant role in introducing dynamic conformational diversity in proteins in a decreasing order of polarity.
The substitutions of the amino acid at the predetermined critical point at the C-terminal of L2 lipase may increase its thermostability and enzymatic activity, or even otherwise speed up the unfolding of the protein structure. The C-terminal of most proteins is often flexible and disordered. However, some protein functions are directly related to flexibility and play significant role in enzyme reaction. The critical point for mutation of L2 lipase structure was predicted at the position 385 of the L2 sequence, and the best three mutants were determined based on I-Mutant2.0 software. The best three mutants were S385E, S385I and S385V. The effects of the substitution of the amino acids at the critical point were analysed with molecular dynamics simulation by using Yet Another Scientific Artificial Reality Application software. The predicted mutant L2 lipases were found to have lower root mean square deviation value as compared to L2 lipase. It was indicated that all the three mutants had higher compactness in the structure, consequently enhanced the stability. Root mean square fluctuation analysis showed that the flexibility of L2 lipase was reduced by mutations. Purified S385E lipase had an optimum temperature of 80 °C in Tris-HCl pH 8. The highest enzymatic activity of purified S385E lipase was obtained at 80 °C temperature in Tris-HCl pH 8, while for L2 lipase it was at 70 °C in Glycine-NaOH pH 9. The thermal stability of S385V lipase was enhanced as compared to other protein since that the melting point (T m) value was at 85.96 °C. S385I lipase was more thermostable compared to recombinant L2 lipase and other mutants at temperature 60 °C within 16 h preincubation.
Polyunsaturated fatty acids (PUFAs) play an important role in human diet. Despite the wide-ranging importance and benefits from heart health to brain functions, humans and mammals cannot synthesize PUFAs de novo. The primary sources of PUFA are fish and plants. Due to the increasing concerns associated with food security as well as issues of environmental contaminants in fish oil, there has been considerable interest in the production of polyunsaturated fatty acids from alternative resources which are more sustainable, safer, and economical. For instance, marine bacteria, particularly the genus of Shewanella, Photobacterium, Colwellia, Moritella, Psychromonas, Vibrio, and Alteromonas, are found to be one among the major microbial producers of polyunsaturated fatty acids. Recent developments in the area with a focus on the production of polyunsaturated fatty acids from marine bacteria as well as the metabolic engineering strategies for the improvement of PUFA production are discussed.
GDSL esterase J15 (EstJ15) is a member of Family II of lipolytic enzyme. The enzyme was further classified in subgroup SGNH hydrolase due to the presence of highly conserve motif, Ser-Gly-Asn-His in four conserved blocks I, II, III, and V, respectively. X-ray quality crystal of EstJ15 was obtained from optimized formulation containing 0.10 M ammonium sulphate, 0.15 M sodium cacodylate trihydrate pH 6.5, and 20% PEG 8000. The crystal structure of EstJ15 was solved at 1.38 Å with one molecule per asymmetric unit. The structure exhibits α/β hydrolase fold and shared low amino acid sequence identity of 23% with the passenger domain of the autotransporter EstA of Pseudomonas aeruginosa. The active site is located at the centre of the structure, formed a narrow tunnel that hinder long substrates to be catalysed which was proven by the protein-ligand docking analysis. This study facilitates the understanding of high substrate specificity of EstJ15 and provide insights on its catalytic mechanism.
The utilization of organic solvents as reaction media for enzymatic reactions provides numerous industrially attractive advantages. However, an adaptation of enzyme towards organic solvent is unpredictable and not fully understood because of limited information on the organic solvent tolerant enzymes. To understand how the enzyme can adapt to the organic solvent environment, structural and computational approaches were employed. A recombinant elastase from Pseudomonas aeruginosa strain K was an organic solvent tolerant zinc metalloprotease was successfully crystallized and diffracted up to 1.39 Å. Crystal structure of elastase from strain K showed the typical, canonical alpha-beta hydrolase fold consisting of 10-helices (118 residues), 10- β-strands (38 residues) and 142 residues were formed other secondary structure such as loop and coil to whole structure. The elastase from Pseusomonas aeruginosa strain K possess His-140, His-144 and Glu-164 served as a ligand for zinc ion. The conserved catalytic triad was composed of Glu-141, Tyr-155 and His-223. Three-dimensional structure features such as calcium-binding and presence of disulphide-bridge contribute to the stabilizing the elastase structure. Molecular dynamic (MD) simulation of elastase revealed that, amino acid residues located at the surface area and disulphide bridge in Cys-30 to Cys-58 were responsible for enzyme stability in organic solvents.
Thermostability remains one of the most desirable traits in many lipases. Numerous studies have revealed promising strategies to improve thermostability and random mutagenesis often leads to unexpected yet interesting findings in engineering stability. Previously, the thermostability of C-terminal truncated cold-adapted lipase from Staphylococcus epidermidis AT2 (rT-M386) was markedly enhanced by directed evolution. The newly evolved mutant, G210C, demonstrated an optimal temperature shift from 25 to 45 °C and stability up to 50 °C. Interestingly, a cysteine residue was randomly introduced on the loop connecting the two lids and accounted for the only cysteine found in the lipase. We further investigated the structural and mechanistic insights that could possibly cause the significant temperature shift. Both rT-M386 and G210C were modeled and simulated at 25 °C and 50 °C. The results clearly portrayed the effect of cysteine substitution primarily on the lid stability. Comparative molecular dynamics simulation analysis revealed that G210C exhibited greater stability than the wild-type at high temperature simulation. The compactness of the G210C lipase structure increased at 50 °C and resulted in enhanced rigidity hence stability. This observation is supported by the improved and stronger non-covalent interactions formed in the protein structure. Our findings suggest that the introduction of a single cysteine residue at the lid region of cold-adapted lipase may result in unexpected increased in thermostability, thus this approach could serve as one of the thermostabilization strategies in engineering lipase stability.
Pseudomonas fluorescens AMS8 lipase lid 1 structure is rigid and holds unclear roles due to the absence of solvent-interactions. Lid 1 region was stabilized by 17 hydrogen bond linkages and displayed lower mean hydrophobicity (0.596) compared to MIS38 lipase. Mutating lid 1 residues, Thr-52 and Gly-55 to aromatic hydrophobic-polar tyrosine would churned more side-chain interactions between lid 1 and water or toluene. This study revealed that T52Y leads G55Y and its recombinant towards achieving higher solvent-accessible surface area and longer half-life at 25 to 37 °C in 0.5% (v/v) toluene. T52Y also exhibited better substrate affinity with long-chain carbon substrate in aqueous media. The affinity for pNP palmitate, laurate and caprylate increased in 0.5% (v/v) toluene in recombinant AMS8, but the affinity in similar substrates was substantially declined in lid 1 mutated lipases. Regarding enzyme efficiency, the recombinant AMS8 lipase displayed highest value of kcat/Km in 0.5% (v/v) toluene, mainly with pNPC. In both hydrolysis reactions with 0% and 0.5% (v/v) toluene, the enzyme efficiency of G55Y was found higher than T52Y for pNPL and pNPP. At 0.5% (v/v) toluene, both mutants showed reductions in activation energy and enthalpy values as temperature increased from 25 to 35 °C, displaying better catalytic functions. Only T52Y exhibited increase in entropy values at 0.5% (v/v) toluene indicating structure stability. As a conclusion, Thr-52 and Gly-55 are important residues for lid 1 stability as their existence helps to retain the geometrical structure of alpha-helix and connecting hinge.
A comparative structure analysis between space- and an Earth-grown T1 recombinant lipase from Geobacillus zalihae had shown changes in the formation of hydrogen bonds and ion-pair interactions. Using the space-grown T1 lipase validated structure having incorporated said interactions, the recombinant T1 lipase was re-engineered to determine the changes brought by these interactions to the structure and stability of lipase. To understand the effects of mutation on T1 recombinant lipase, five mutants were developed from the structure of space-grown T1 lipase and biochemically characterized. The results demonstrate an increase in melting temperature up to 77.4 °C and 76.0 °C in E226D and D43E, respectively. Moreover, the mutated lipases D43E and E226D had additional hydrogen bonds and ion-pair interactions in their structures due to the improvement of stability, as observed in a longer half-life and an increased melting temperature. The biophysical study revealed differences in β-Sheet percentage between less stable (T118N) and other mutants. As a conclusion, the comparative analysis of the tertiary structure and specific residues associated with ion-pair interactions and hydrogen bonds could be significant in revealing the thermostability of an enzyme with industrial importance.
Surface charge residues have been recognized as one of the stability determinants in protein. In this study, we sought to compare and analyse the stability and conformational dynamics of staphylococcal lipase mutants with surface lysine mutation using computational and experimental methods. Three highly mutable and exposed lysine residues (Lys91, Lys177, Lys325) were targeted to generate six mutant lipases in silico. The model structures were simulated in water environment at 25 °C. Our simulations showed that the stability was compromised when Lys177 was substituted while mutation at position 91 and 325 improved the stability. To illustrate the putative alterations of enzyme stability in the stabilising mutants, we characterized single mutant K325G and double mutant K91A/K325G. Both mutants showed a 5 °C change in optimal temperature compared to their wild type. Single mutant K325G rendered a longer half-life at 25 °C (T1/2 = 21 h) while double mutant K91A/K325G retained only 40% of relative activity after 12 h incubation. The optimal pH for mutant K325G was shifted from 8 to 9 and similar substrate preference was observed for the wild type and two mutants. Our findings indicate that surface lysine mutation alters the enzymatic behaviour and, thus, rationalizes the functional effects of surface exposed lysine in conformational stability and activity of this lipase.
Screening for a new yeast as an alternative host is expected to solve the limitations in the present yeast expression system. A yeast sample which was isolated from the traditional food starter 'ragi' from Malaysia was identified to contain Meyerozyma guilliermondii strain SMB. This yeast-like fungus strain SMB was characterized to assess its suitability as an expression host. Lipase activity was absent in this host (when assayed at 30 °C and 70 °C) and Hygromycin B (50 μg/mL) was found to be its best selection marker. Then, the hyg gene (Hygromycin B) was used to replace the sh ble gene (Zeocin) expression cassette in a Komagataella phaffii expression vector (designated as pFLDhα). A gene encoding the mature thermostable lipase from Bacillus sp. L2 was cloned into pFLDhα, followed by transformation into strain SMB. The optimal expression of L2 lipase was achieved using YPTM (Yeast Extract-Peptone-Tryptic-Methanol) medium after 48 h with 0.5% (v/v) methanol induction, which was 3 times faster than another K. phaffii expression system. In conclusion, a new host-vector system was established as a platform to express L2 lipase under the regulation of PFLD1. It could also be promising to express other recombinant proteins without inducers.
The conversion of aldehydes to valuable alkanes via cyanobacterial aldehyde deformylating oxygenase is of great interest. The availability of fossil reserves that keep on decreasing due to human exploitation is worrying, and even more troubling is the combustion emission from the fuel, which contributes to the environmental crisis and health issues. Hence, it is crucial to use a renewable and eco-friendly alternative that yields compound with the closest features as conventional petroleum-based fuel, and that can be used in biofuels production. Cyanobacterial aldehyde deformylating oxygenase (ADO) is a metal-dependent enzyme with an α-helical structure that contains di‑iron at the active site. The substrate enters the active site of every ADO through a hydrophobic channel. This enzyme exhibits catalytic activity toward converting Cn aldehyde to Cn-1 alkane and formate as a co-product. These cyanobacterial enzymes are small and easy to manipulate. Currently, ADOs are broadly studied and engineered for improving their enzymatic activity and substrate specificity for better alkane production. This review provides a summary of recent progress in the study of the structure and function of ADO, structural-based engineering of the enzyme, and highlight its potential in producing biofuels.
The deposition of paraffin wax in crude oil is a problem faced by the oil and gas industry during extraction, transportation, and refining of crude oil. Most of the commercialized chemical additives to prevent wax are expensive and toxic. As an environmentally friendly alternative, this study aims to find a novel thermophilic bacterial strain capable of degrading paraffin wax in crude oil to control wax deposition. To achieve this, the biodegradation of crude oil paraffin wax by 11 bacteria isolated from seawater and oil-contaminated soil samples was investigated at 70°C. The bacteria were identified as Geobacillus kaustophilus N3A7, NFA23, DFY1, Geobacillus jurassicus MK7, Geobacillus thermocatenulatus T7, Parageobacillus caldoxylosilyticus DFY3 and AZ72, Anoxybacillus geothermalis D9, Geobacillus stearothermophilus SA36, AD11, and AD24. The GCMS analysis showed that strains N3A7, MK7, DFY1, AD11, and AD24 achieved more than 70% biodegradation efficiency of crude oil in a short period (3 days). Notably, most of the strains could completely degrade C37-C40 and increase the ratio of C14-C18, especially during the initial 2 days incubation. In addition, the degradation of crude oil also resulted in changes in the pH of the medium. The degradation of crude oil is associated with the production of degradative enzymes such as alkane monooxygenase, alcohol dehydrogenase, lipase, and esterase. Among the 11 strains, the highest activities of alkane monooxygenase were recorded in strain AD24. A comparatively higher overall alcohol dehydrogenase, lipase, and esterase activities were observed in strains N3A7, MK7, DFY1, AD11, and AD24. Thus, there is a potential to use these strains in oil reservoirs, crude oil processing, and recovery to control wax deposition. Their ability to withstand high temperature and produce degradative enzymes for long-chain hydrocarbon degradation led to an increase in the short-chain hydrocarbon ratio, and subsequently, improving the quality of the oil.
Fatty acid desaturase catalyzes the desaturation reactions by insertion of double bonds into the fatty acyl chain, producing unsaturated fatty acids. Though soluble fatty acid desaturases have been studied widely in advanced organisms, there are very limited studies of membrane fatty acid desaturases due to the difficulty of generating recombinant desaturase. Brassica napus is a rapeseed, which possesses a range of different membrane-bound desaturases capable of producing fatty acids including Δ3, Δ4, Δ8, Δ9, Δ12, and Δ15 fatty acids. The 1155 bp open reading frame of Δ12 fatty acid desaturase (FAD12) from Brassica napus codes for 383 amino acid residues with a molecular weight of 44 kDa. It was expressed in Escherichia coli at 37 °C in soluble and insoluble forms when induced with 0.5 mM IPTG. Soluble FAD12 has been purified using Ni2+-Sepharose affinity chromatography with a total protein yield of 0.728 mg/mL. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that desaturase activity of FAD12 could produce linoleic acid from oleic acid at a retention time of 17.6 with a conversion rate of 47%. Characterization of purified FAD12 revealed the optimal temperature of FAD12 was 50 °C with 2 mM preferred substrate concentration of oleic acid. Analysis of circular dichroism (CD) showed FAD12 was made up of 47.3% and 0.9% of alpha-helix and β-sheet secondary structures. The predicted Tm value was 50.2 °C.
Carboxylesterases (CEs) are members of prominent esterase, and as their name imply, they catalyze the cleavage of ester linkages. By far, a considerable number of novel CEs have been identified to investigate their exquisite physiological and biochemical properties. They are abundant enzymes in nature, widely distributed in relatively broad temperature range and in various sources; both macroorganisms and microorganisms. Given the importance of these enzymes in broad industries, interest in the study of their mechanisms and structural-based engineering are greatly increasing. This review presents the current state of knowledge and understanding about the structure and functions of this ester-metabolizing enzyme, primarily from bacterial sources. In addition, the potential biotechnological applications of bacterial CEs are also encompassed. This review will be useful in understanding the molecular basis and structural protein of bacterial CEs that are significant for the advancement of enzymology field in industries.