Single Residue Substitution at N-Terminal Affects Temperature Stability and Activity of L2 Lipase

In Silico Analysis and Development of the Secretory Expression of D-Psicose-3-Epimerase in Escherichia coli

D-psicose-3-epimerase (DPEase), a key enzyme for D-psicose production, has been successfully expressed in Escherichia coli with high yield. However, intracellular expression results in high downstream processing costs and greater risk of lipopolysaccharide (LPS) contamination during cell disruption. The secretory expression of DPEase could minimize the number of purification steps and prevent LPS contamination, but achieving the secretion expression of DPEase in E. coli is challenging and has not been reported due to certain limitations. This study addresses these challenges by enhancing the secretion of DPEase in E. coli through computational predictions and structural analyses. Signal peptide prediction identified PelB as the most effective signal peptide for DPEase localization and enhanced solubility. Supplementary strategies included the addition of 0.1% (v/v) Triton X-100 to promote protein secretion, resulting in higher extracellular DPEase (0.5 unit/mL). Low-temperature expression (20 °C) mitigated the formation of inclusion bodies, thus enhancing DPEase solubility. Our findings highlight the pivotal role of signal peptide selection in modulating DPEase solubility and activity, offering valuable insights for protein expression and secretion studies, especially for rare sugar production. Ongoing exploration of alternative signal peptides and refinement of secretion strategies promise further enhancement in enzyme secretion efficiency and process safety, paving the way for broader applications in biotechnology.

Lipases for targeted industrial applications, focusing on the development of biotechnologically significant aspects: A comprehensive review of recent trends in protein engineering

Lipases are remarkable biocatalysts, adept at catalyzing the breakdown of diverse compounds into glycerol, fatty acids, and mono- and di-glycerides via hydrolysis. Beyond this, they facilitate esterification, transesterification, alcoholysis, acidolysis, and more, making them versatile in industrial applications. In industrial processes, lipases that exhibit high stability are favored as they can withstand harsh conditions. However, most native lipases are unable to endure adverse conditions, making them unsuitable for industrial use. Protein engineering proves to be a potent technology in the development of lipases that can function effectively under challenging conditions and fulfill criteria for various industrial processes. This review concentrated on new trends in protein engineering to enhance the diversity of lipase genes and employed in silico methods for predicting and comprehensively analyzing target mutations in lipases. Additionally, key molecular factors associated with industrial characteristics of lipases, including thermostability, solvent tolerance, catalytic activity, and substrate preference have been elucidated. The present review delved into how industrial traits can be enhanced through directed evolution (epPCR, gene shuffling), rational design (FRESCO, ASR), combined engineering strategies (i.e. CAST, ISM, and FRISM) as protein engineering methodologies in contexts of biodiesel production, food processing, and applications of detergent, pharmaceutics, and plastic degradation.

Enhanced Thermostability of Nattokinase by Computation-Based Rational Redesign of Flexible Regions

Nattokinase is a nutrient in healthy food natto that has the function of preventing and treating blood thrombus. However, its low thermostability and fibrinolytic activity limit its application in food and pharmaceuticals. In this study, we used bioinformatics analysis to identify two loops (loop10 and loop12) in the flexible region of nattokinase rAprY. Using this basis, we screened the G131S-S161T variant, which showed a 2.38-fold increase in half-life at 55 °C, and the M3 variant, which showed a 2.01-fold increase in activity, by using a thermostability prediction algorithm. Bioinformatics analysis revealed that the enhanced thermostability of the G131S-S161T variant was due to the increased rigidity and structural shrinkage of the overall structure. Additionally, the increased rigidity of the local region surrounding the active center and its mutated sites helps maintain its normal conformation in high-temperature environments. The increased catalytic activity of the M3 variant may be due to its more efficient substrate binding mechanism. We investigated strategies to improve the thermostability and fibrinolytic activity of nattokinase, and the resulting variants show promise for industrial production and application.

Effects of alcohol concentration and temperature on the dynamics and stability of mutant Staphylococcal lipase

The stability and activity of lipase in organic media are important parameters in determining how quickly biocatalysis proceeds. This study aimed to examine the effects of two commonly used alcohols in industrial applications, methanol (MtOH) and ethanol (EtOH) on the conformational stability and catalytic activity of G210C lipase, a laboratory-evolved mutant of Staphylococcus epidermidis AT2 lipase. Simulation studies were performed using an open-form predicted structure under 30, 40 and 50% of MtOH and EtOH at 25 °C and 45 °C. The overall enzyme structure becomes more flexible with increasing concentration of MtOH and exhibited the highest flexibility in 40% EtOH. In EtOH, the movement of the lid was found to be temperature-dependent with a noticeable shift in the lid position at 45 °C. Lid opening was evidenced at 50% of MtOH and EtOH which was supported by the increase in SASA of hydrophobic residues of the lid and catalytic triad. The active site remained mostly intact. An open-closed lid transition was observed when the structure was re-simulated in water. Experimental evaluation of the lipase stability showed that the half-life reduced when the enzyme was treated with 40% (v/v) and 50% (v/v) of EtOH and MtOH respectively. The finding implies that a high concentration of alcohol and elevated temperature can induce the lid opening of lipase which could be essential for the activation of the enzyme, provided that the catalytic performance in the active site is not compromised.Communicated by Ramaswamy H. Sarma.

Recent advances in simultaneous thermostability-activity improvement of industrial enzymes through structure modification

Engineered thermostable microbial enzymes are widely employed to catalyze chemical reactions in numerous industrial sectors. Although high thermostability is a prerequisite of industrial applications, enzyme activity is usually sacrificed during thermostability improvement. Therefore, it is vital to select the common and compatible strategies between thermostability and activity improvement to reduce mutants̕ libraries and screening time. Three functional protein engineering approaches, including directed evolution, rational design, and semi-rational design, are employed to manipulate protein structure on a genetic basis. From a structural standpoint, integrative strategies such as increasing substrate affinity; introducing electrostatic interaction; removing steric hindrance; increasing flexibility of the active site; N- and C-terminal engineering; and increasing intramolecular and intermolecular hydrophobic interactions are well-known to improve simultaneous activity and thermostability. The current review aims to analyze relevant strategies to improve thermostability and activity simultaneously to circumvent the thermostability and activity trade-off of industrial enzymes.

Altering the Regioselectivity of T1 Lipase from Geobacillus zalihae toward sn-3 Acylglycerol Using a Rational Design Approach

The regioselectivity characteristic of lipases facilitate a wide range of novel molecule unit constructions and fat modifications. Lipases can be categorized as sn-1,3, sn-2, and random regiospecific. Geobacillus zalihae T1 lipase catalyzes the hydrolysis of the sn-1,3 acylglycerol chain. The T1 lipase structural analysis shows that the oxyanion hole F16 and its lid domain undergo structural rearrangement upon activation. Site-directed mutagenesis was performed by substituting the lid domain residues (F180G and F181S) and the oxyanion hole residue (F16W) in order to study their effects on the structural changes and regioselectivity. The novel lipase mutant 3M switches the regioselectivity from sn-1,3 to only sn-3. The mutant 3M shifts the optimum pH to 10, alters selectivity toward p-nitrophenyl ester selectivity to C14-C18, and maintains a similar catalytic efficiency of 518.4 × 10−6 (s−1/mM). The secondary structure of 3M lipase comprises 15.8% and 26.3% of the α-helix and β-sheet, respectively, with a predicted melting temperature (Tm) value of 67.8 °C. The in silico analysis was conducted to reveal the structural changes caused by the F180G/F181S/F16W mutations in blocking the binding of the sn-1 acylglycerol chain and orientating the substrate to bond to the sn-3 acylglycerol, which resulted in switching the T1 lipase regioselectivity.

Discovery of the Key Mutation Site Influencing the Thermostability of Thermomyces lanuginosus Lipase by Rosetta Design Programs

Lipases are remarkable biocatalysts and are broadly applied in many industry fields because of their versatile catalytic capabilities. Considering the harsh biotechnological treatment of industrial processes, the activities of lipase products are required to be maintained under extreme conditions. In our current study, Gibbs free energy calculations were performed to predict potent thermostable Thermomyces lanuginosus lipase (TLL) variants by Rosetta design programs. The calculating results suggest that engineering on R209 may greatly influence TLL thermostability. Accordingly, ten TLL mutants substituted R209 were generated and verified. We demonstrate that three out of ten mutants (R209H, R209M, and R209I) exhibit increased optimum reaction temperatures, melting temperatures, and thermal tolerances. Based on molecular dynamics simulation analysis, we show that the stable hydrogen bonding interaction between H198 and N247 stabilizes the local configuration of the 250-loop in the three R209 mutants, which may further contribute to higher rigidity and improved enzymatic thermostability. Our study provides novel insights into a single residue, R209, and the 250-loop, which were reported for the first time in modulating the thermostability of TLL. Additionally, the resultant R209 variants generated in this study might be promising candidates for future-industrial applications.

Thermostability engineering of industrial enzymes through structure modification

Thermostability is an essential requirement of enzymes in the industrial processes to catalyze the reactions at high temperatures; thus, enzyme engineering through directed evolution, semi-rational design and rational design are commonly employed to construct desired thermostable mutants. Several strategies are implemented to fulfill enzymes' thermostability demand including decreasing the entropy of the unfolded state through substitutions Gly → Xxx or Xxx → Pro, hydrogen bond, salt bridge, introducing two different simultaneous interactions through single mutant, hydrophobic interaction, filling the hydrophobic cavity core, decreasing surface hydrophobicity, truncating loop, aromatic-aromatic interaction and introducing positively charged residues to enzyme surface. In the current review, horizons about compatibility between secondary structures and substitutions at preferable structural positions to generate the most desirable thermostability in industrial enzymes are broadened. KEY POINTS: • Protein engineering is a powerful tool for generating thermostable industrial enzymes. • Directed evolution and rational design are practical approaches in enzyme engineering. • Substitutions in preferable structural positions can increase thermostability.

Crucial Residues of C-Terminal Oligopeptide C60 to Improve the Yield of Prebiotic Xylooligosaccharides by Truncated Mutation

Increasing the yields of short xylooligosaccharides by enzymatic production is efficient to improve prebiotic effects. Previously, C-terminal oligopeptide C60 was found to accelerate short xylooligosaccharides. Herein, in order to further understand the molecular mechanism of C60, the sequence analysis firstly showed that C60 displays typical properties of a linker (rich in proline/alanine/glycine/glutamine/arginine, 8.33–20.00%). C60 shared the highest identity with the N-terminal region of esterase (98.33%) and high identity with the linker between xylanase and esterase from Prevotella sp. (56.50%), it is speculated to originate from an early linker between XynA and another domain. Besides, structure simulation showed that C60 enhances the molecular interactions between substrate and active residues to improve catalytic efficiency. Moreover, three truncated variants with different lengths of C-terminal regions were successfully generated in Escherichia coli. The specific activities of variants were 6.44–10.24 fold of that of XynA-Tr, and their optimal temperature and pH were the same as XynA-Tr. Three truncated variants released more xylooligosaccharides, especially xylobiose (46.33, 43.41, and 49.60%), than XynA-Tr (32.43%). These results are helpful to understand the molecular mechanism of C60, and also provide new insight to improve the yields of short xylooligosaccharides by molecular modification at the terminal of xylanases.