Identification and recombinant expression of a cutinase from Papiliotrema laurentii that hydrolyzes natural and synthetic polyesters

Given the multitude of extracellular enzymes at their disposal, many of which are designed to degrade nature's polymers (lignin, cutin, cellulose, etc.), fungi are adept at targeting synthetic polyesters with similar chemical composition. Microbial-influenced deterioration of xenobiotic polymeric surfaces is an area of interest for material scientists as these are important for the conservation of the underlying structural materials. Here, we describe the isolation and characterization of the Papiliotrema laurentii 5307AH (P. laurentii) cutinase, Plcut1. P. laurentii is basidiomycete yeast with the ability to disperse Impranil-DLN (Impranil), a colloidal polyester polyurethane, in agar plates. To test whether the fungal factor involved in this clearing was a secreted enzyme, we screened the ability of P. laurentii culture supernatants to disperse Impranil. Using size exclusion chromatography (SEC), we isolated fractions that contained Impranil-clearing activity. These fractions harbored a single ~22 kD band, which was excised and subjected to peptide sequencing. Homology searches using the peptide sequences identified, revealed that the protein Papla1 543643 (Plcut1) displays similarities to serine esterase and cutinase family of proteins. Biochemical assays using recombinant Plcut1 confirmed that this enzyme has the capability to hydrolyze Impranil, soluble esterase substrates, and apple cutin. Finally, we confirmed the presence of the Plcut1 in culture supernatants using a custom antibody that specifically recognizes this protein. The work shown here supports a major role for the Plcut1 in the fungal degradation of natural polyesters and xenobiotic polymer surfaces.IMPORTANCEFungi play a vital role in the execution of a broad range of biological processes that drive ecosystem function through production of a diverse arsenal of enzymes. However, the universal reactivity of these enzymes is a current problem for the built environment and the undesired degradation of polymeric materials in protective coatings. Here, we report the identification and characterization of a hydrolase from Papiliotrema laurentii 5307AH, an aircraft-derived fungal isolate found colonizing a biodeteriorated polymer-coated surface. We show that P. laurentii secretes a cutinase capable of hydrolyzing soluble esters as well as ester-based compounds forming solid surface coatings. These findings indicate that this fungus plays a significant role in biodeterioration through the production of a cutinase adept at degrading ester-based polymers, some of which form the backbone of protective surface coatings. The work shown here provides insights into the mechanisms employed by fungi to degrade xenobiotic polymers.

Enzymes as indispensable markers in disease diagnosis

Enzymes have been used for disease diagnosis for many decades; however, advancements in technology like ELISA and flow cytometry-based detection have significantly increased their use and have increased the sensitivity of detection. Technological advancements in recombinant enzyme production have increased enzymatic stability, and the use of colorimetric-based and florescence-based assays has led to their increased use as biomarkers for disease detection. Enzymes like acid phosphatase, cathepsin, lactate dehydrogenase, thymidine kinase and creatine kinase are indispensable markers for diagnosing cancer, cardiovascular diseases and others. This minireview summarizes various enzymes used in disease diagnosis, their metabolic role, market value and potential as disease markers across various metabolic and other disorders.

Enhancing the Enantioselectivity and Catalytic Efficiency of Esterase from Bacillus subtilis for Kinetic Resolution of l-Menthol through Semirational Design

Enzymatic kinetic resolution is a promising way to produce l-menthol. However, the properties of the reported biocatalysts are still unsatisfactory and far from being ready for industrial application. Herein, a para-nitrobenzylesterase (pnbA) gene from Bacillus subtilis was cloned and expressed to produce l-menthol from d,l-menthyl acetate. The highest enantiomeric excess (ee) value of the product generated by pnbA was only approximately 80%, with a high conversion rate (47.8%) of d,l-menthyl acetate with the help of a cosolvent, indicating high catalytic activity but low enantioselectivity (E = 19.95). To enhance the enantioselectivity and catalytic efficiency of pnbA to d,l-menthyl acetate in an organic solvent-free system, site-directed mutagenesis was performed based on the results of molecular docking. The F314E/F315T mutant showed the best catalytic properties (E = 36.25) for d,l-menthyl acetate, with 92.11% ee and 30.58% conversion of d,l-menthyl acetate. To further improve the properties of pnbA, additional mutants were constructed based on the structure-guided triple-code saturation mutagenesis strategy. Finally, four mutants were screened for the best enantioselectivity (ee > 99%, E > 300) and catalytic efficiency at a high substrate concentration (200 g/L) without a cosolvent. This work provides several generally applicable biocatalysts for the industrial production of l-menthol.

Role of the C-Terminal β Sandwich of Thermoanaerobacter tengcongensis Thermophilic Esterase in Hydrolysis of Long-Chain Acyl Substrates

To search for a novel thermostable esterase for optimized industrial applications, esterase from a thermophilic eubacterium species, Thermoanaerobacter tengcongensis MB4, was purified and characterized in this work. Sequence analysis of T. tengcongensis esterase with other homologous esterases of the same family revealed an apparent tail at the C-terminal that is not conserved across the esterase family. Hence, it was hypothesized that the tail is unlikely to have an essential structural or catalytic role. However, there is no documented report of any role for this tail region. We probed the role of the C-terminal domain on the catalytic activity and substrate preference of T. tengcongensis esterase EstA3 with a view to see how it could be engineered for enhanced properties. To achieve this, we cloned, expressed, and purified the wild-type and the truncated versions of the enzyme. In addition, a naturally occurring member of the family (from Brevibacillus brevis) that lacks the C-terminal tail was also made. In vitro characterization of the purified enzymes showed that the C-terminal domain contributes significantly to the catalytic activity and distinct substrate preference of T. tengcongensis esterase EstA3. All three recombinant enzymes showed the highest preference for paranitrophenyl butyrate (pNPC4), which suggests they are true esterases, not lipases. Kinetic data revealed that truncation had a slight effect on the substrate-binding affinity. Thus, the drop in preference towards long-chain substrates might not be a result of substrate binding affinity alone. The findings from this work could form the basis for future protein engineering allowing the modification of esterase catalytic properties through domain swapping or by attaching a modular protein domain.

Application of liquid-based colorimetric method for high throughput screening of bioplastic-degrading strains using esterase assay

To alleviate environmental problems caused by using conventional plastics, bioplastics have garnered significant interest as alternatives to petroleum-based plastics. Despite possessing better degradability traits compared to traditional plastics, the degradation of bioplastics still demands a longer duration than initially anticipated. This necessitates the utilization of degradation strains or enzymes to enhance degradation efficiency, ensuring timely degradation. In this study, a novel screening method to identify bioplastic degraders faster was suggested to circumvent the time-consuming and laborious characteristics of solid-based plate assays. This liquid-based colorimetric method confirmed the extracellular esterase activity with p-nitrophenyl esters. It eliminated the needs to prepare plastic emulsion plates at the initial screening system, shortening the time for the overall screening process and providing more quantitative data. p-nitrophenyl hexanoate (C6) was considered the best substrate among the various p-nitrophenyl esters as substrates. The screening was performed in liquid-based 96-well plates, resulting in the discovery of a novel strain, Bacillus sp. SH09, with a similarity of 97.4% with Bacillus licheniformis. Furthermore, clear zone assays, degradation investigations, scanning electron microscopy, and gel permeation chromatography were conducted to characterize the biodegradation capabilities of the new strain, the liquid-based approach offered a swift and less labor-intensive option during the initial stages.

MEnTaT: A machine-learning approach for the identification of mutations to increase protein stability

Enhancing protein thermal stability is important for biomedical and industrial applications as well as in the research laboratory. Here, we describe a simple machine-learning method which identifies amino acid substitutions that contribute to thermal stability based on comparison of the amino acid sequences of homologous proteins derived from bacteria that grow at different temperatures. A key feature of the method is that it compares the sequences based not simply on the amino acid identity, but rather on the structural and physicochemical properties of the side chain. The method accurately identified stabilizing substitutions in three well-studied systems and was validated prospectively by experimentally testing predicted stabilizing substitutions in a polyamine oxidase. In each case, the method outperformed the widely used bioinformatic consensus approach. The method can also provide insight into fundamental aspects of protein structure, for example, by identifying how many sequence positions in a given protein are relevant to temperature adaptation.

Macrolide esterases: current threats and opportunities

Antibiotics often contain ester bonds. The macrocyclic lactones of macrolides are pre-eminent examples in which ester bonds are essential to the form and function of antibiotics. Bacterial macrolide esterases that hydrolyze these macrocyclic lactones to confer antimicrobial resistance (AMR) are the topic of this forum. We provide insight into their role in agricultural systems and discuss their emergence and their potential extensibility to bioremediation efforts.

Biochemical and Cellular Characterization of the Function of Fluorophosphonate-Binding Hydrolase H (FphH) in Staphylococcus aureus Support a Role in Bacterial Stress Response

The development of new treatment options for bacterial infections requires access to new targets for antibiotics and antivirulence strategies. Chemoproteomic approaches are powerful tools for profiling and identifying novel druggable target candidates, but their functions often remain uncharacterized. Previously, we used activity-based protein profiling in the opportunistic pathogen Staphylococcus aureus to identify active serine hydrolases termed fluorophosphonate-binding hydrolases (Fph). Here, we provide the first characterization of S. aureus FphH, a conserved, putative carboxylesterase (referred to as yvaK in Bacillus subtilis) at the molecular and cellular level. First, phenotypic characterization of fphH-deficient transposon mutants revealed phenotypes during growth under nutrient deprivation, biofilm formation, and intracellular survival. Biochemical and structural investigations revealed that FphH acts as an esterase and lipase based on a fold well suited to act on a small to long hydrophobic unbranched lipid group within its substrate and can be inhibited by active site-targeting oxadiazoles. Prompted by a previous observation that fphH expression was upregulated in response to fusidic acid, we found that FphH can deacetylate this ribosome-targeting antibiotic, but the lack of FphH function did not infer major changes in antibiotic susceptibility. In conclusion, our results indicate a functional role of this hydrolase in S. aureus stress responses, and hypothetical functions connecting FphH with components of the ribosome rescue system that are conserved in the same gene cluster across Bacillales are discussed. Our atomic characterization of FphH will facilitate the development of specific FphH inhibitors and probes to elucidate its physiological role and validity as a drug target.

Enhanced Activity and Stability of an Acetyl Xylan Esterase in Hydrophilic Alcohols through Site-Directed Mutagenesis

Current demands for the development of suitable biocatalysts showing high process performance is stimulated by the need to replace current chemical synthesis with cleaner alternatives. A drawback to the use of biocatalysts for unique applications is their low performance in industrial conditions. Hence, enzymes with improved performance are needed to achieve innovative and sustainable biocatalysis. In this study, we report the improved performance of an engineered acetyl xylan esterase (BaAXE) in a hydrophilic organic solvent. The structure of BaAXE was partitioned into a substrate-binding region and a solvent-affecting region. Using a rational design approach, charged residues were introduced at protein surfaces in the solvent-affecting region. Two sites present in the solvent-affecting region, A12D and Q143E, were selected for site-directed mutagenesis, which generated the mutants MUT12, MUT143 and MUT12-143. The mutants MUT12 and MUT143 reported lower Km (0.29 mM and 0.27 mM, respectively) compared to the wildtype (0.41 mM). The performance of the mutants in organic solvents was assessed after enzyme incubation in various strengths of alcohols. The mutants showed improved activity and stability compared to the wild type in low strengths of ethanol and methanol. However, the activity of MUT143 was lost in 40% methanol while MUT12 and MUT12-143 retained over 70% residual activity in this environment. Computational analysis links the improved performance of MUT12 and MUT12-143 to novel intermolecular interactions that are absent in MUT143. This work supports the rationale for protein engineering to augment the characteristics of wild-type proteins and provides more insight into the role of charged residues in conferring stability.

Resistance risk assessment of six pyrethroids and acephate toward the resistant adult tarnished plant bug, Lygus lineolaris

Due to rapidly developed resistance, pest management relies less on pyrethroids to control economically damaging infestations of the tarnished plant bug (TPB), Lygus lineolaris (Palisot de Beauvois) in cotton fields of Mississippi. Yet, pyrethroid resistance remains prevalent in TPB populations. This study assessed the resistance levels in adult TPB to six common pyrethroids and acephate. Resistant TBPs were collected from wild host plants in late October after harvest in the Mississippi Delta region of the United States. Based on LC50 values, the field-resistant TPBs displayed higher resistance to permethrin, esfenvalerate, and bifenthrin (approximately 30 fold) and moderate resistance to λ-cyhalothrin, β-cyfluthrin, ζ-cypermethrin, and acephate (approximately 15 fold). Further investigations showed that the inhibitors of three detoxification enzyme, triphenyl phosphate (TPP), diethyl maleate (DEM), and piperonyl butoxide (PBO) had synergistic effects on permethrin, λ-cyhalothrin, and bifenthrin in resistant TPBs. Furthermore, elevated esterase, GST, and P450 activities were significantly expressed in field-resistant TPBs. Additionally, GST and esterase were reduced after 48 h exposure to certain pyrethroids at LC50 dose. The synergistic and biochemical assays consistently indicated that P450 and esterase were involved in pyrethroid detoxification in TPBs. This study provides valuable information for the continued use of pyrethroids and acephate in controlling TPBs in cotton fields in the Mississippi Delta region of the United States.

Root-knot nematode assessment: species identification, distribution, and new host records in Portugal

Considered one of the most devastating plant parasitic nematodes worldwide, Meloidogyne spp. (commonly known as the root-knot nematodes (RKNs)) are obligate sedentary endoparasites that establish in the roots, causing hyperplasia and hypertrophy of surrounding cells, triggering the formation of galls. These galls will affect root development and physiology, leading to substantial yield losses. During 2017-2022, an extensive survey of Meloidogyne species was undertaken in Portugal (mainland and islands). A total of 1,071 samples were collected by the National Plant Protection Organization (DGAV) and private farmers from different regions of the country and were analysed at the Laboratory of Nematology (NemaINIAV). Samples in which the presence of Meloidogyne sp. was detected were used to perform bioassays to obtain females and juveniles for further studies. Since the accurate identification of RKNs is an important aspect of crop management, morphological and biochemical characterisation was performed. The most common morphological features were observed, showing consistency with previous descriptions of the genus. The biochemical identification using the esterase (EST) phenotype revealed the phenotypes of Meloidogyne arenaria, M enterolobi, M. hispanica, M. hapla, M. incognita, M javanica, and M. luci. Meloidogyne incognita and M. javanica were found to be the most prevalent species in the different regions followed by M. arenaria and M. hapla. This is the first distribution report performed in Portugal on RKNs, contributing to the development of management strategies and to updated information on the status of these pests in Europe.

C-Terminal β8-α9 Interaction Modulates Thermal Stability and Enzymatic Activity Differently in Hyperthermophilic Esterase EstE1 and Mesophilic Esterase rPPE

Hydrophobic interactions and hydrogen bonds are 2 types of noncovalent interactions that play distinct roles in the folding and structural stability of proteins. However, the specific roles of these interactions in hydrophobic or hydrophilic environments in α/β-hydrolases are not fully understood. A hyperthermophilic esterase EstE1 in a dimer maintains the C-terminal β8-α9 strand-helix via hydrophobic interactions (Phe276 and Leu299), constituting a closed dimer interface. Moreover, a mesophilic esterase rPPE in a monomer maintains the same strand-helix via a hydrogen bond (Tyr281 and Gln306). Unpaired polar residues (F276Y in EstE1 and Y281A/F and Q306A in rPPE) or reduced hydrophobic interactions (F276A/L299A in EstE1) between the β8-α9 strand-helix decrease thermal stability. EstE1 (F276Y/L299Q) and rPPE WT, both with the β8-α9 hydrogen bond, showed the same thermal stability as EstE1 WT and rPPE (Y281F/Q306L), which possess hydrophobic interactions instead. However, EstE1 (F276Y/L299Q) and rPPE WT exhibited higher enzymatic activity than EstE1 WT and rPPE (Y281F/Q306L), respectively. This suggests that α/β-hydrolases favor the β8-α9 hydrogen bond for catalytic activity in monomers or oligomers. Overall, these findings demonstrate how α/β-hydrolases modulate hydrophobic interactions and hydrogen bonds to adapt to different environments. Both types of interactions contribute equally to thermal stability, but the hydrogen bond is preferred for catalytic activity. IMPORTANCE Esterases hydrolyze short to medium-chain monoesters and contain a catalytic His on a loop between the C-terminal β8-strand and α9-helix. This study explores how hyperthermophilic esterase EstE1 and mesophilic esterase rPPE adapt to different temperatures by utilizing the β8-α9 hydrogen bonds or hydrophobic interactions differently. EstE1 forms a hydrophobic dimer interface, while rPPE forms a monomer stabilized by a hydrogen bond. The study demonstrates that these enzymes stabilize β8-α9 strand-helix differently but achieve similar thermal stability. While the β8-α9 hydrogen bond or hydrophobic interactions contribute equally to thermal stability, the hydrogen bond provides higher activity due to increased catalytic His loop flexibility in both EstE1 and rPPE. These findings reveal how enzymes adapt to extreme environments while maintaining their functions and have implications for engineering enzymes with desired activities and stabilities.

Evidence-based insecticide resistance in South American tomato leaf miner, Phthorimaea absoluta (Meyrick) under laboratory selection

The South American tomato moth, Phthorimaea absoluta (Meyrick), is one of the key pests of tomato in India. Since its report in 2014, chemical control has been the main means of tackling this pest, both in the open field and protected cultivation. Despite regular insecticidal sprays, many outbreaks were reported from major tomato-growing regions of South India during 2019-2020. A study was conducted to investigate the effect of insecticide resistance on biology, biochemical enzymes, and gene expression in various P. absoluta field populations viz., Bangalore, Kolar, Madurai, Salem, and Anantapur to commonly used insecticides such as flubendiamide, cyantraniliprole, and indoxacarb. Increased levels of insecticide resistance ratios (RR) were recorded in P. absoluta populations of different locations. A significant increase in cytochrome P450 monooxygenase (CYP/MFO) and esterase levels was noticed in the resistant population compared to susceptible one. Through molecular studies, we identified four new CYP genes viz., CYP248f (flubendiamide), CYP272c, CYP724c (cyantraniliprole), and CYP648i (indoxacarb). The expression levels of these genes significantly increased as the folds of resistance increased from G1 to G20 (generation), indicating involvement of the identified genes in insecticide resistance development in P. absoluta. In addition, the resistant populations showed decreased fecundity, increased larval development period, and adult longevity, resulting in more crop damage. The information generated in the present study thus helps in understanding the development of insecticide resistance by P. absoluta and suggests the farmers and researchers to use insecticides wisely by adopting insecticide resistance management as a strategy under integrated pest management.

Aldehyde-Based Inhibitors of the Peptidoglycan O-Acetylesterase Ape

The O-acetylation of the muramic acid residues in peptidoglycan (PG) is a modification that protects the bacteria from lysis due to the action of lysozyme.  In Gram-negative bacteria, deacetylation is required to allow lytic transglycosylases to promote PG cleavage during cell growth and division.  This deacetylation is catalyzed by O-acetylpeptidoglycan esterase (Ape) which is a serine esterase and employs covalent catalysis via a serine-linked acyl enzyme intermediate.  Loss of Ape activity affects the size and shape of bacteria and dramatically reduces virulence.  In this work, we report the first rationally designed aldehyde-based inhibitors of Ape from Campylobacter jejuni.  The most potent of these acts as a competitive inhibitor with a Ki value of 13 mM.  We suspect that the inhibitors are forming adducts with the active site serine that closely mimic the tetrahedral intermediate of the normal catalytic cycle.  Support for this notion is found in the observation that reduction of the aldehyde to an alcohol effectively abolishes the inhibition.

Detect Cytochrome C Oxidase- and Glutathione-S-Transferase-Mediated Detoxification in a Permethrin-Resistant Population of Lygus lineolaris

Frequent sprays on cotton prompted resistance development in the tarnished plant bug (TPB). Knowledge of global gene regulation is highly desirable to better understand resistance mechanisms and develop molecular tools for monitoring and managing resistance. Novel microarray expressions of 6688 genes showed 3080 significantly up- or down-regulated genes in permethrin-treated TPBs. Among the 1543 up-regulated genes, 255 code for 39 different enzymes, and 15 of these participate in important pathways and metabolic detoxification. Oxidase is the most abundant and over-expressed enzyme. Others included dehydrogenases, synthases, reductases, and transferases. Pathway analysis revealed several oxidative phosphorylations associated with 37 oxidases and 23 reductases. One glutathione-S-transferase (GST LL_2285) participated in three pathways, including drug and xenobiotics metabolisms and pesticide detoxification. Therefore, a novel resistance mechanism of over-expressions of oxidases, along with a GST gene, was revealed in permethrin-treated TPB. Reductases, dehydrogenases, and others may also indirectly contribute to permethrin detoxification, while two common detoxification enzymes, P450 and esterase, played less role in the degradation of permethrin since none was associated with the detoxification pathway. Another potential novel finding from this study and our previous studies confirmed multiple/cross resistances in the same TPB population with a particular set of genes for different insecticide classes.

Genome-wide identification, classification, and expression profiling of serine esterases and other esterase-related proteins in the tobacco hornworm, Manduca sexta

Serine esterases (SEs) are hydrolases that catalyze the conversion of carboxylic esters into acids and alcohols. Lipases and carboxylesterases constitute two major groups of SEs. Although over a hundred of insect genomes are known, systematic identification and classification of SEs are rarely performed, likely due to large size and complex composition of the gene family in each species. Considering their key roles in lipid metabolism and other physiological processes, we have categorized 144 M. sexta SEs and SE homologs (SEHs), 114 of which contain a motif of GXSXG. Multiple sequence alignment and phylogenetic tree analysis have revealed 39 neutral lipases (NLs), 3 neutral lipase homologs (NLHs), 11 acidic lipases (ALs), 3 acidic lipase homologs (ALHs), a lipase-3, a triglyceride lipase, a monoglyceride lipase, a hormone-sensitive lipase, and a GDSL lipase. Eighty-three carboxylesterase genes encode 29 α-esterases (AEs), 12 AEHs (e.g., SEH4-1-3), 20 feruloyl esterases (FEs), 2 FEHs, 2 β-esterases (BEs), 2 integument esterases (IEs), 1 IEH, 4 juvenile hormone esterases, 2 acetylcholinesterases, gliotactin, 6 neuroligins, neurotactin, and an uncharacteristic esterase homolog. In addition to these GXSXG proteins, we have identified 26 phospholipases and 13 thioesterases. Expression profiling of these genes in specific tissues and stages has provided insights into their functions including digestion, detoxification, hormone processing, neurotransmission, reproduction, and developmental regulation. In summary, we have established a framework of information on SEs and related proteins in M. sexta to stimulate their research in the model species and comparative investigations in agricultural pests or disease vectors.

Solid-State Fermentation of Trichoderma spp.: A New Way to Valorize the Agricultural Digestate and Produce Value-Added Bioproducts

In this study, the agricultural digestate from anaerobic biogas production mixed with food wastes was used as a substrate to grow Trichoderma reesei RUT-C30 and Trichoderma atroviride Ta13 in solid-state fermentation (SSF) and produce high-value bioproducts, such as bioactive molecules to be used as ingredients for biostimulants. The Trichoderma spp. reached their maximum growth after 6 and 3 SSF days, respectively. Both Trichoderma species were able to produce cellulase, esterase, and citric and malic acids, while T. atroviride also produced gibberellins and oxylipins as shown by ultraperformance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) profiling. Experimental evaluation of germination parameters highlighted a significant promotion of tomato seed germination and root elongation induced by T. atroviride crude extracts from SSF. This study suggests an innovative sustainable use of the whole digestate mixed with agro-food waste as a valuable substrate in fungal biorefineries. Here, it has been applied to produce plant growth-promoting fungi and bioactive molecules for sustainable agriculture.

A neglected and emerging antimicrobial resistance gene encodes for a serine-dependent macrolide esterase

The discovery of unreported antimicrobial resistance genes (ARGs) remains essential. Here, we report the identification and preliminary characterization of an α/β-hydrolase that inactivates macrolides. This serine-dependent macrolide esterase co-occurs with emerging ARGs in the environment, animal microbiomes, and pathogens.

The Mobility of the Cap Domain Is Essential for the Substrate Promiscuity of a Family IV Esterase from Sorghum Rhizosphere Microbiome

Metagenomics offers the possibility to screen for versatile biocatalysts. In this study, the microbial community of the Sorghum bicolor rhizosphere was spiked with technical cashew nut shell liquid, and after incubation, the environmental DNA (eDNA) was extracted and subsequently used to build a metagenomic library. We report the biochemical features and crystal structure of a novel esterase from the family IV, EH₀, retrieved from an uncultured sphingomonad after a functional screen in tributyrin agar plates. EH₀ (optimum temperature [T_opt], 50°C; melting temperature [T_m], 55.7°C; optimum pH [pH_opt], 9.5) was stable in the presence of 10 to 20% (vol/vol) organic solvents and exhibited hydrolytic activity against p-nitrophenyl esters from acetate to palmitate, preferably butyrate (496 U mg^-1), and a large battery of 69 structurally different esters (up to 30.2 U mg^-1), including bis(2-hydroxyethyl)-terephthalate (0.16 ± 0.06 U mg^-1). This broad substrate specificity contrasts with the fact that EH₀ showed a long and narrow catalytic tunnel, whose access appears to be hindered by a tight folding of its cap domain. We propose that this cap domain is a highly flexible structure whose opening is mediated by unique structural elements, one of which is the presence of two contiguous proline residues likely acting as possible hinges, which together allow for the entrance of the substrates. Therefore, this work provides a new role for the cap domain, which until now was thought to be an immobile element that contained hydrophobic patches involved in substrate prerecognition and in turn substrate specificity within family IV esterases. IMPORTANCE A better understanding of structure-function relationships of enzymes allows revelation of key structural motifs or elements. Here, we studied the structural basis of the substrate promiscuity of EH₀, a family IV esterase, isolated from a sample of the Sorghum bicolor rhizosphere microbiome exposed to technical cashew nut shell liquid. The analysis of EH₀ revealed the potential of the sorghum rhizosphere microbiome as a source of enzymes with interesting properties, such as pH and solvent tolerance and remarkably broad substrate promiscuity. Its structure resembled those of homologous proteins from mesophilic Parvibaculum and Erythrobacter spp. and hyperthermophilic Pyrobaculum and Sulfolobus spp. and had a very narrow, single-entry access tunnel to the active site, with access controlled by a capping domain that includes a number of nonconserved proline residues. These structural markers, distinct from those of other substrate-promiscuous esterases, can help in tuning substrate profiles beyond tunnel and active site engineering.

Screening Enzymes That Can Depolymerize Commercial Biodegradable Polymers: Heterologous Expression of Fusarium solani Cutinase in Escherichia coli

In recent years, a number of microbial enzymes capable of degrading plastics have been identified. Biocatalytic depolymerization mediated by enzymes has emerged as a potentially more efficient and environmentally friendly alternative to the currently employed methods for plastic treatment and recycling. However, the functional and systematic study of depolymerase enzymes with respect to the degradation of a series of plastic polymers in a single work has not been widely addressed at present. In this study, the ability of a set of enzymes (esterase, arylesterase and cutinase) to degrade commercial biodegradable polymers (PBS, PBAT, PHB, PHBH, PHBV, PCL, PLA and PLA/PCL) and the effect of pre-treatment methods on their degradation rate was assessed. The degradation products were identified and quantified by HPLC and LC-HRMS analysis. Out of the three enzymes, Fusarium solani cutinase (FsCut) showed the highest activity on grinded PBAT, PBS and PCL after 7 days of incubation. FsCut was engineered and heterologous expressed in Escherichia coli, which conferred the bacterium the capability of degrading solid discs of PBAT and to grow in PBS as the sole carbon source of the medium.

EstG is a novel esterase required for cell envelope integrity in Caulobacter

Proper regulation of the bacterial cell envelope is critical for cell survival. Identification and characterization of enzymes that maintain cell envelope homeostasis is crucial, as they can be targets for effective antibiotics. In this study, we have identified a novel enzyme, called EstG, whose activity protects cells from a variety of lethal assaults in the ⍺-proteobacterium Caulobacter crescentus. Despite homology to transpeptidase family cell wall enzymes and an ability to protect against cell-wall-targeting antibiotics, EstG does not demonstrate biochemical activity toward cell wall substrates. Instead, EstG is genetically connected to the periplasmic enzymes OpgH and BglX, responsible for synthesis and hydrolysis of osmoregulated periplasmic glucans (OPGs), respectively. The crystal structure of EstG revealed similarities to esterases and transesterases, and we demonstrated esterase activity of EstG in vitro. Using biochemical fractionation, we identified a cyclic hexamer of glucose as a likely substrate of EstG. This molecule is the first OPG described in Caulobacter and establishes a novel class of OPGs, the regulation and modification of which are important for stress survival and adaptation to fluctuating environments. Our data indicate that EstG, BglX, and OpgH comprise a previously unknown OPG pathway in Caulobacter. Ultimately, we propose that EstG is a novel enzyme that instead of acting on the cell wall, acts on cyclic OPGs to provide resistance to a variety of cellular stresses.

Exploring Potent Fungal Isolates from Sanitary Landfill Soil for In Vitro Degradation of Dibutyl Phthalate

Di-n-butyl phthalate (DBP) is one of the most extensively used plasticizers for providing elasticity to plastics. Being potentially harmful to humans, investigating eco-benign options for its rapid degradation is imperative. Microbe-mediated DBP mineralization is well-recorded, but studies on the pollutant's fungal catabolism remain scarce. Thus, the present investigation was undertaken to exploit the fungal strains from toxic sanitary landfill soil for the degradation of DBP. The most efficient isolate, SDBP4, identified on a molecular basis as Aspergillus flavus, was able to mineralize 99.34% dibutyl phthalate (100 mg L^-1) within 15 days of incubation. It was found that the high production of esterases by the fungal strain was responsible for the degradation. The strain also exhibited the highest biomass (1615.33 mg L^-1) and total soluble protein (261.73 µg mL^-1) production amongst other isolates. The DBP degradation pathway scheme was elucidated with the help of GC-MS-based characterizations that revealed the formation of intermediate metabolites such as benzyl-butyl phthalate (BBP), dimethyl-phthalate (DMP), di-iso-butyl-phthalate (DIBP) and phthalic acid (PA). This is the first report of DBP mineralization assisted with A. flavus, using it as a sole carbon source. SDBP4 will be further formulated to develop an eco-benign product for the bioremediation of DBP-contaminated toxic sanitary landfill soils.

Biochemical characterization of an acetylesterase from Bacillus subtilis and its application for 7-aminocephalosporanic acid deacetylation

Deacetyl-7-aminocephalosporanic acid (D-7-ACA), which could be converted from 7-aminocephalosporanic acid (7-ACA), is a crucial starting material that is used for synthesizing industrial semisynthetic β-lactam antibiotics. Enzymes involved in the conversion from 7-ACA to D-7-ACA present critical resources in the pharmaceutical industry. In the present study, a putative acetylesterase, EstSJ, identified from Bacillus subtilis KATMIRA1933, was first heterologously expressed in Escherichia coli BL21(DE3) cells and biochemically characterized. EstSJ belongs to carbohydrate esterase family 12 and is active on short-chain acyl esters from p-NPC₂ to p-NPC₆. Multiple sequence alignments showed that EstSJ was also an SGNH family esterase with a typical GDS(X) motif at its N-terminal end and a catalytic triad composed of Ser¹⁸⁶-Asp³⁵⁴-His³⁵⁷. The purified EstSJ displayed the highest specific activity of 1,783.52 U mg^-1 at 30°C and pH 8.0, and was stable within the pH range of 5.0-11.0. EstSJ can deacetylate the C3' acetyl group of 7-ACA to generate D-7-ACA, and the deacetylation activity was 4.50 U mg^-1. Based on the structural and molecular docking with 7-ACA, the catalytic active sites (Ser¹⁸⁶-Asp³⁵⁴-His³⁵⁷) together with four substrate-binding residues (Asn²⁵⁹, Arg²⁹⁵, Thr³⁵⁵, and Leu³⁵⁶) of EstSJ are revealed. This study provided a promising 7-ACA deacetylase candidate that could be applied to produce D-7-ACA from 7-ACA in the pharmaceutical industry.

Hydrolysis Mechanism of Carbamate Methomyl by a Novel Esterase PestE: A QM/MM Approach

Methomyl is one of the most important carbamates that has caused potential hazardous effects on both human beings and the environment. Here, we systematically investigated the hydrolysis mechanism of methomyl catalyzed by esterase PestE using molecular dynamics simulations (MD) and quantum mechanics/molecular mechanics (QM/MM) calculations. The hydrolysis mechanism involves two elementary steps: (Ⅰ) serine-initiated nucleophilic attack and (Ⅱ) C-O bond cleavage. Our work elicits the atomic level details of the hydrolysis mechanism and free energy profiles along the reaction pathway. The Boltzmann-weighted average potential barriers are 19.1 kcal/mol and 7.5 kcal/mol for steps Ⅰ and Ⅱ, respectively. We identified serine-initiated nucleophilic attack as the rate determining-step. The deep learning-based k_cat prediction model indicated that the barrier of the rate-determining step is 15.4 kcal/mol, which is in good agreement with the calculated results using Boltzmann-weighted average method. We have elucidated the importance of the protein-substrate interactions and the roles of the key active site residues during the hydrolysis process through noncovalent interactions analysis and electrostatic potential (ESP) analysis. The results provide practical value for achieving efficient degradation of carbamates by hydrolases.

Changes in Key Aroma Compounds and Esterase Activity of Monascus-Fermented Cheese across a 30-Day Ripening Period

Monascus-fermented cheese (MC) is a new type of mold-ripened cheese that combines a traditional Chinese fermentation fungus, Monascus purpureus M1, with Western cheese fermentation techniques. In this study, the compositions of the volatile aroma compounds in MC were analyzed during a 30-day ripening period using SPME-Arrow and GC-O-MS. The activity of esterase in MC, which is a key enzyme catalyzing esterification reaction, was determined and compared with the control group (CC). Next, sensory analysis was conducted via quantitative descriptive analysis followed by Pearson correlation analysis between esterase activity and the key flavor compounds. A total of 76 compounds were detected. Thirty-three of these compounds could be smelled at the sniffing port and were identified as the key aroma compounds. The esterase activity in MC was found to be 1.24~1.33 times that of the CC. Moreover, the key odor features of ripened MC were alcohol and fruity flavors, considerably deviating from the sour and cheesy features found for the ripened CC. Furthermore, correlation analysis showed that esterase activity was strongly correlated (|r|> 0.75, p < 0.05) with various acids such as pentanoic and nonanoic acids and several aromatic esters, namely, octanoic acid ethyl ester and decanoic acid ethyl ester, revealing the key role that esterases play in developing the typical aroma of ripened MC.

Cold-Active Lipases and Esterases: A Review on Recombinant Overexpression and Other Essential Issues

Cold environments characterised by diverse temperatures close to or below the water freezing point dominate about 80% of the Earth's biosphere. One of the survival strategies adopted by microorganisms living in cold environments is their expression of cold-active enzymes that enable them to perform an efficient metabolic flux at low temperatures necessary to thrive and reproduce under those constraints. Cold-active enzymes are ideal biocatalysts that can reduce the need for heating procedures and improve industrial processes' quality, sustainability, and cost-effectiveness. Despite their wide applications, their industrial usage is still limited, and the major contributing factor is the lack of complete understanding of their structure and cold adaptation mechanisms. The current review looked at the recombinant overexpression, purification, and recent mechanism of cold adaptation, various approaches for purification, and three-dimensional (3D) crystal structure elucidation of cold-active lipases and esterase.

Vicagrel is hydrolyzed by Raf kinase inhibitor protein in human intestine

As an analog of clopidogrel and prasugrel, vicagrel is completely hydrolyzed to intermediate thiolactone metabolite 2-oxo-clopidogrel (also the precursor of active thiol metabolite H4) in human intestine, predominantly by AADAC and CES2; however, other unknown vicagrel hydrolases remain to be identified. In this study, recombinant human Raf kinase inhibitor protein (rhRKIP) and pooled human intestinal S9 (HIS9) fractions and microsome (HIM) preparations were used as the different enzyme sources; prasugrel as a probe drug for RKIP (a positive control), vicagrel as a substrate drug of interest, and the rate of the formation of thiolactone metabolites 2-oxo-clopidogrel and R95913 as metrics of hydrolase activity examined, respectively. In addition, an IC₅₀ value of inhibition of rhRKIP-catalyzed vicagrel hydrolysis by locostatin was measured, and five classical esterase inhibitors with distinct esterase selectivity were used to dissect the involvement of multiple hydrolases in vicagrel hydrolysis. The results showed that rhRKIP hydrolyzed vicagrel in vitro, with the values of K_m , V_max , and CL_int measured as 20.04 ± 1.99 μM, 434.60 ± 12.46 nM/min/mg protein, and 21.69 ± 0.28 ml/min/mg protein, respectively, and that an IC₅₀ value of locostatin was estimated as 1.24 ± 0.04 mM for rhRKIP. In addition to locostatin, eserine and vinblastine strongly suppressed vicagrel hydrolysis in HIM. It is concluded that RKIP can catalyze the hydrolysis of vicagrel in the human intestine, and that vicagrel can be hydrolyzed by multiple hydrolases, such as RKIP, AADAC, and CES2, concomitantly.

Chemical and Enzymatic Characterization of Leaves from Spanish Table Olive Cultivars

Olive leaves are generated as by-products in the olive industry and contain substances with biological properties that provide health benefits. Although these compounds have been characterized in many leaves from olive cultivars devoted to olive oil extraction, few data are available on leaves from the processing of table olives. In this study, the concentration of polyphenols, triterpenic acids, sugars and enzymatic activities (polyphenol oxidase, peroxidase, β-glucosidase and esterase) were determined in the leaves of the olive tree (Olea europaea L.) of cvs. Aloreña, Cacereña, Empeltre, Hojiblanca, Manzanilla, Verdial, Gordal and Morona. The mean total phenolic content in olive leaves reached 75.58 g/kg fresh weight, and oleuropein was the main polyphenol identified (89.7-96.5%). The main triterpenic acid identified was oleanolic acid, and the main sugar was mannitol, with mean values of 15.83 and 22.31 g/kg, respectively. However, the content of these biocompounds was influenced by the type of cultivar and the orchards of origin. The highest oleuropein content was found in the Manzanilla variety, while the Gordal had the highest triterpene and mannitol content. In particular, the phenolic content could also be affected by endogenous enzymatic activities. High polyphenol oxidase, peroxidase and β-glucosidase activity and low esterase activity were detected, compared to the fruit. Similar to the phenolic compounds, enzymatic activities varied with the harvesting season. The lowest phenolic content corresponded to the highest polyphenol oxidase activity detected during spring. The rest of the enzymatic activities also varied throughout the year, but no common trend was observed.

Systematic evaluation of agarose- and agar-based bioinks for extrusion-based bioprinting of enzymatically active hydrogels

Extrusion-based 3D bioprinting enables the production of customized hydrogel structures that can be employed in flow reactors when printing with enzyme-containing inks. The present study compares inks based on either low-melt agarose or agar at different concentrations (3-6%) and loaded with the thermostable enzyme esterase 2 from the thermophilic organism Alicyclobacillus acidocaldarius (AaEst2) with regard to their suitability for the fabrication of such enzymatically active hydrogels. A customized printer setup including a heatable nozzle and a cooled substrate was established to allow for clean and reproducible prints. The inks and printed hydrogel samples were characterized using rheological measurements and compression tests. All inks were found to be sufficiently printable to create lattices without overhangs, but printing quality was strongly enhanced at 4.5% polymer or more. The produced hydrogels were characterized regarding mechanical strength and diffusibility. For both properties, a strong correlation with polymer concentration was observed with highly concentrated hydrogels being more stable and less diffusible. Agar hydrogels were found to be more stable and show higher diffusion rates than comparable agarose hydrogels. Enzyme leaching was identified as a major drawback of agar hydrogels, while hardly any leaching from agarose hydrogels was detected. The poor ability of agar hydrogels to permanently immobilize enzymes indicates their limited suitability for their employment in perfused biocatalytic reactors. Batch-based activity assays showed that the enzymatic activity of agar hydrogels was roughly twice as high as the activity of agarose hydrogels which was mostly attributed to the increased amount of enzyme leaching. Agarose bioinks with at least 4.5% polymer were identified as the most suitable of the investigated inks for the printing of biocatalytic reactors with AaEst2. Drawbacks of these inks are limited mechanical and thermal stability, not allowing the operation of a reactor at the optimum temperature of AaEst2 which is above the melting point of the employed low-melt agarose.

Design and Characterization of In-One Protease-Esterase PluriZyme

Proteases are abundant in prokaryotic genomes (~10 per genome), but their recovery encounters expression problems, as only 1% can be produced at high levels; this value differs from that of similarly abundant esterases (1-15 per genome), 50% of which can be expressed at good levels. Here, we design a catalytically efficient artificial protease that can be easily produced. The PluriZyme EH1AB1 with two active sites supporting the esterase activity was employed. A Leu24Cys mutation in EH1AB1, remodelled one of the esterase sites into a proteolytic one through the incorporation of a catalytic dyad (Cys24 and His214). The resulting artificial enzyme, EH1AB1C, efficiently hydrolysed (azo)casein at pH 6.5-8.0 and 60-70 °C. The presence of both esterase and protease activities in the same scaffold allowed the one-pot cascade synthesis (55.0 ± 0.6% conversion, 24 h) of L-histidine methyl ester from the dipeptide L-carnosine in the presence of methanol. This study demonstrates that active sites supporting proteolytic activity can be artificially introduced into an esterase scaffold to design easy-to-produce in-one protease-esterase PluriZymes for cascade reactions, namely, the synthesis of amino acid esters from dipeptides. It is also possible to design artificial proteases with good production yields, in contrast to natural proteases that are difficult to express.

Crystal structure of a family VIII β-lactamase fold hydrolase reveals the molecular mechanism for its broad substrate scope

Family VIII esterases present similarities to class C β-lactamases, which show nucleophilic serines located at the S-X-X-K motif instead of the G-X-S-X-G or G-D-S-(L) motif shown by other carboxylesterase families. Here, we report the crystal structure of a novel family VIII (subfamily VIII. I) esterase (EH₇ ; denaturing temperature, 52.6 ± 0.3 °C; pH optimum 7.0-9.0) to deepen its broad substrate range. Indeed, the analysis of the substrate specificity revealed its capacity to hydrolyse nitrocefin as a model chromogenic cephalosporin substrate (40.4 ± 11.4 units·g^-1 ), and a large battery of 66 structurally different esters (up to 1730 min^-1 ), including bis(2-hydroxyethyl)-terephthalate (241.7 ± 8.5 units·g^-1 ) and the mycotoxin T-2 (1220 ± 52 units·g^-1 ). It also showed acyltransferase activity through the synthesis of benzyl 3-oxobutanoate (40.4 ± 11.4 units·g^-1 ) from benzyl alcohol and vinyl acetoacetate. Such a broad substrate scope is rare among family VIII esterases and lipolytic enzymes. Structural analyses of free and substrate-bound forms of this homooctamer esterase suggest that EH₇ presents a more opened and exposed S1 site having no steric hindrance for the entrance of substrates to the active site, more flexible R1, R2 and R3 regions allowing for the binding of a wide spectrum of substrates into the active site, and small residues in the conserved motif Y-X-X containing the catalytic Tyr enabling the entrance of large substrates. These unique structural elements in combination with docking experiments allowed us to gain valuable insights into the substrate specificity of this esterase and possible others belonging to family VIII.

Catalytically Active Amyloids as Future Bionanomaterials

Peptides and proteins can aggregate into highly ordered and structured conformations called amyloids. These supramolecular structures generally have convergent features, such as the formation of intermolecular beta sheets, that lead to fibrillary architectures. The resulting fibrils have unique mechanical properties that can be exploited to develop novel nanomaterials. In recent years, sequences of small peptides have been rationally designed to self-assemble into amyloids that catalyze several chemical reactions. These amyloids exhibit reactive surfaces that can mimic the active sites of enzymes. In this review, I provide a state-of-the-art summary of the development of catalytically active amyloids. I will focus especially on catalytic activities mediated by hydrolysis, which are the most studied examples to date, as well as novel types of recently reported activities that promise to expand the possible repertoires. The combination of mechanical properties with catalytic activity in an amyloid scaffold has great potential for the development of future bionanomaterials aimed at specific applications.

Trypanosoma brucei Acyl-Protein Thioesterase-like (TbAPT-L) Is a Lipase with Esterase Activity for Short and Medium-Chain Fatty Acids but Has No Depalmitoylation Activity

Dynamic post-translational modifications allow the rapid, specific, and tunable regulation of protein functions in eukaryotic cells. S-acylation is the only reversible lipid modification of proteins, in which a fatty acid, usually palmitate, is covalently attached to a cysteine residue of a protein by a zDHHC palmitoyl acyltransferase enzyme. Depalmitoylation is required for acylation homeostasis and is catalyzed by an enzyme from the alpha/beta hydrolase family of proteins usually acyl-protein thioesterase (APT1). The enzyme responsible for depalmitoylation in Trypanosoma brucei parasites is currently unknown. We demonstrate depalmitoylation activity in live bloodstream and procyclic form trypanosomes sensitive to dose-dependent inhibition with the depalmitoylation inhibitor, palmostatin B. We identified a homologue of human APT1 in Trypanosoma brucei which we named TbAPT-like (TbAPT-L). Epitope-tagging of TbAPT-L at N- and C- termini indicated a cytoplasmic localization. Knockdown or over-expression of TbAPT-L in bloodstream forms led to robust changes in TbAPT-L mRNA and protein expression but had no effect on parasite growth in vitro, or cellular depalmitoylation activity. Esterase activity in cell lysates was also unchanged when TbAPT-L was modulated. Unexpectedly, recombinant TbAPT-L possesses esterase activity with specificity for short- and medium-chain fatty acid substrates, leading to the conclusion, TbAPT-L is a lipase, not a depalmitoylase.

Development of Esterase-Resistant and Highly Active Ghrelin Analogs via Thiol-Ene Click Chemistry

The orexigenic peptide ghrelin exerts important functions in energy metabolism and has therapeutic potential to treat certain diseases. Native ghrelin carries an essential O-fatty acyl moiety; however, this post-translational modification is susceptible to hydrolysis by certain esterases in circulation, representing a major route of its in vivo inactivation. In the present study, we developed a novel approach to prepare various esterase-resistant ghrelin analogs via photoinduced thiol-ene click chemistry. A recombinant unacylated human ghrelin mutant was reacted with commercially available terminal alkenes; thus, various alkyl moieties were introduced to the side chain of its unique Cys3 residue via a thioether bond. Among 11 S-alkylated ghrelin analogs, analog 11, generated by reacting with 2-methyl-1-octene, not only acquired much higher stability in serum but also retained full activity compared with native human ghrelin. Thus, the present study provided an efficient approach to prepare highly stable and highly active ghrelin analogs with therapeutic potential.

Esterases as emerging biocatalysts: Mechanistic insights, genomic and metagenomic, immobilization, and biotechnological applications

Esterase enzymes are a family of hydrolases that catalyze the breakdown and formation of ester bonds. Esterases have gained a prominent position in today's world's industrial enzymes market. Due to their unique biocatalytic attributes, esterases contribute to environmentally sustainable design approaches, including biomass degradation, food and feed industry, dairy, clothing, agrochemical (herbicides, insecticides), bioremediation, biosensor development, anticancer, antitumor, gene therapy, and diagnostic purposes. Esterases can be isolated by a diverse range of mammalian tissues, animals, and microorganisms. The isolation of extremophilic esterases increases the interest of researchers in the extraction and utilization of these enzymes at the industrial level. Genomic, metagenomic, and immobilization techniques have opened innovative ways to extract esterases and utilize them for a longer time to take advantage of their beneficial activities. The current study discusses the types of esterases, metagenomic studies for exploring new esterases, and their biomedical applications in different industrial sectors.

Escherichia coli YigI is a Conserved Gammaproteobacterial Acyl-CoA Thioesterase Permitting Metabolism of Unusual Fatty Acid Substrates

Thioesterases play a critical role in metabolism, membrane biosynthesis, and overall homeostasis for all domains of life. In this present study, we characterize a putative thioesterase from Escherichia coli MG1655 and define its role as a cytosolic enzyme. Building on structure-guided functional predictions, we show that YigI is a medium- to long-chain acyl-CoA thioesterase that is involved in the degradation of conjugated linoleic acid (CLA) in vivo, showing overlapping specificity with two previously defined E. coli thioesterases TesB and FadM. We then bioinformatically identify the regulatory relationships that induce YigI expression, which include: an acidic environment, high oxygen availability, and exposure to aminoglycosides. Our findings define a role for YigI and shed light on why the E. coli genome harbors numerous thioesterases with closely related functions. IMPORTANCE Previous research has shown that long chain acyl-CoA thioesterases are needed for E. coli to grow in the presence of carbon sources such as conjugated linoleic acid, but that E. coli must possess at least one such enzyme that had not previously been characterized. Building off structure-guided function predictions, we showed that the poorly annotated protein YigI is indeed the previously unidentified third acyl CoA thioesterase. We found that the three potentially overlapping acyl-CoA thioesterases appear to be induced by nonoverlapping conditions and use that information as a starting point for identifying the precise reactions catalyzed by each such thioesterase, which is an important prerequisite for their industrial application and for more accurate metabolic modeling of E. coli.

Functional and Transcriptome Analysis of Streptococcus pyogenes Virulence on Loss of Its Secreted Esterase

Esterases are broadly expressed in bacteria, but much remains unknown about their pathogenic effect. In previous studies, we focused on an esterase secreted by Streptococcus pyogenes (group A Streptococcus, GAS). Streptococcal secreted esterase (Sse) can hydrolyze the sn−2 ester bonds of platelet−activating factor (PAF), converting it to an inactive form that inhibits neutrophil chemotaxis to the infection sites. However, as a virulent protein, Sse probably participates in GAS pathogenesis far beyond chemotaxis inhibition. In this study, we generated the sse gene knockout strain (Δsse) from the parent strain MGAS5005 (hypervirulent M1T1 serotype) and compared the difference in phenotypes. Absence of Sse was related to weakened skin invasion in a murine infection model, and significantly reduced GAS epithelial adherence, invasion, and intracellular survival. Reduced virulence of the Δsse mutant strain was explored through transcriptome analysis, revealing a striking reduction in the abundance of invasive virulence factors including M protein, SIC, ScpA, and SclA. Besides the influence on the virulence, Sse also affected carbohydrate, amino acid, pyrimidine, and purine metabolism pathways. By elucidating Sse−mediated pathogenic process, the study will contribute to the development of new therapeutic agents that target bacterial esterases to control clinical GAS infections.

Species differences in liver microsomal hydrolysis of acyl glucuronide in humans and rats

Acyl glucuronides (AGs) are known as one of the causes of idiosyncratic drug toxicity (IDT). Although AGs can be enzymatically hydrolysed by β-glucuronidase and esterase, much information on their characteristics and species differences is lacking. This study was aimed to clarify species differences in AG hydrolysis between human and rat liver microsomes (HLM and RLM).To evaluate the AG hydrolysis profile, and the contribution of β-glucuronidase and esterase towards AG hydrolysis in HLM and RLM, nonsteroidal anti-inflammatory drugs (NSAIDs) were used. AGs were incubated with 0.1 M Tris-HCl buffer (pH 7.4) and 0.3 mg/mL HLM or RLM in the absence or presence of β-glucuronidase inhibitor, D-saccharic acid 1,4-lactone (D-SL) and esterase inhibitor, phenylmethylsulfonyl fluoride (PMSF).AGs of mefenamic acid (MEF-AG) and etodolac (ETO-AG) showed significantly higher AG hydrolysis rates in RLM than in HLM. Esterases were found to serve as AG hydrolases dominantly in HLM, whereas both esterases and β-glucuronidase equally contribute to AG hydrolysis in RLM. However, MEF-AG and ETO-AG were hydrolysed only by β-glucuronidase.We demonstrated for the first time that the activity of AG hydrolases towards NSAID-AGs differs between humans and rats.

Characterization of Microbial Diversity in Decayed Wood from a Spanish Forest: An Environmental Source of Industrially Relevant Microorganisms

Rotting wood is inhabited by a large diversity of bacteria, fungi, and insects with complex environmental relationships. The aim of this work was to study the composition of the microbiota (bacteria and fungi) in decaying wood from a northwest Spanish forest as a source of industrially relevant microorganisms. The analyzed forest is situated in a well-defined biogeographic area combining Mediterranean and temperate macrobioclimates. Bacterial diversity, determined by metagenome analyses, was higher than fungal heterogeneity. However, a total of 194 different cultivable bacterial isolates (mainly Bacillaceae, Streptomycetaceae, Paenibacillaceae, and Microbacteriaceae) were obtained, in contrast to 343 fungal strains (mainly Aspergillaceae, Hypocreaceae, and Coniochaetaceae). Isolates traditionally known as secondary metabolite producers, such as Actinobacteria and members of the Penicillium genus, were screened for their antimicrobial activity by the detection of antibiotic biosynthetic clusters and competitive bioassays against fungi involved in wood decay. In addition, the ability of Penicillium isolates to degrade cellulose and release ferulic acid from wood was also examined. These results present decaying wood as an ecologically rich niche and a promising source of biotechnologically interesting microorganisms.

Characterization of a Novel Esterase Est33 From an Antarctic Bacterium: A Representative of a New Esterase Family

Studies of microorganisms from extreme environments can sometimes reveal novel proteins with unique properties. Here, we identified a novel esterase gene (Est33) from an Antarctic bacterium. The protein was expressed and purified for biochemical characterizations. Site-mutation variants including S94A, D205A, and H233A were constructed to explore the structure–function relationship of the catalytic triad of Est33, and we found mutating Ser⁹⁴, Asp²⁰⁵, and His²³³ residues lead to a complete loss of enzyme activity. In addition, the catalytic Ser⁹⁴ located in a conserved pentapeptide motif GVSWG. Phylogenetic analysis showed that Est33 and its closely related homologs belonged to an independent group apart from other known family members, indicating that Est33 represented a new family of esterase. The Est33 enzyme was found to be a cold-active esterase retaining 25%–100% activity from 10°C to 30°C and to have optimal catalytic activity toward p-nitrophenol acetate (30°C and pH7.5). The serine modifying reagent phenylmethylsulfonyl fluoride inhibited the activity of Est33 by 77.34%, while thiol reagents such as dithiol threitol (DTT) activated the enzyme by 3-fold. Metal chelating reagents EDTA had no effects, indicating that Est33 is not a metalloenzyme. Collectively, these results indicate that Est33 constitutes the first member of a novel esterase family XXI that has been identified.

Erratum: Cytoplasmic Lipases-A Novel Class of Fungal Defense Proteins Against Nematodes

[This corrects the article DOI: 10.3389/ffunb.2021.696972.].

Evaluation of the Impact of Esterases and Lipases from the Circulatory System against Substrates of Different Lipophilicity

Esterases and lipases can process amphiphilic esters used as drugs and prodrugs and impact their pharmacokinetics and biodistribution. These hydrolases can also process ester components of drug delivery systems (DDSs), thus triggering DDSs destabilization with premature cargo release. In this study we tested and optimized assays that allowed us to quantify and compare individual esterase contributions to the degradation of substrates of increased lipophilicity and to establish limitations in terms of substrates that can be processed by a specific esterase/lipase. We have studied the impact of carbonic anhydrase; phospholipases A1, A2, C and D; lipoprotein lipase; and standard lipase on the hydrolysis of 4-nitrophenyl acetate, 4-nitrophenyl palmitate, DGGR and POPC liposomes, drawing structure–property relationships. We found that the enzymatic activity of these proteins was highly dependent on the lipophilicity of the substrate used to assess them, as expected. The activity observed for classical esterases was diminished when lipophilicity of the substrate increased, while activity observed for lipases generally increased, following the interfacial activation model, and was highly dependent on the type of lipase and its structure. The assays developed allowed us to determine the most sensitive methods for quantifying enzymatic activity against substrates of particular types and lipophilicity.

Expression, Characterization, Fermentation, Immobilization, and Application of a Novel Esterase Est804 From Metagenomic Library in Pesticide Degradation

Esterase, as a type of powerful catabolic enzyme for the degradation of pyrethroid pesticides (PYRs), appears promising in improving the quality of crops and the environment contaminated by pesticide residues. The purpose of this research is to provide a detailed introduction to the enzymatic properties, optimal production and immobilization conditions, and the degradation ability of Est804 for PYRs. The study on enzymatic properties indicated that Est804 was an alkaline esterase with an optimal pH of 8.0 and a broad optimal temperature in the range of 35-50°C. The optimal activity of free Est804 was calculated to be 112.812 U, and the specific enzyme activity was 48.97 U/mg. The kinetic parameters of Est804 were K _m = 0.613 mM, k _cat = 12,371 s^-1, and V _m = 0.095 mM/min. The results of the fermentative optimization demonstrated that the optimal conditions included 1.5% of inoculation amount, 30 mL of liquid volume, 28°C of the fermentation temperature, and 18 h of the fermentation time. The optimal medium consists of 15.87 g of yeast powder, 8.00 g of glycerol, and 9.57 g of tryptone in 1 L of liquid. The optimized enzyme activity was 1.68-fold higher than that before optimization. Immobilized Est804 exhibited the highest activity under the optimum preparation conditions, including 0.35 g of chitosan dosage, 0.4 mL of an enzyme, and 4 h at 40°C for adsorption. The degradation rates of Cypermethrin (CYP), fenpropathrin (FE), and lambda-cyhalothrin (LCT) by Est804 within 30 min were 77.35%, 84.73%, and 74.16%, respectively. The present study indicated that Est804 possesses great potential for the treatment of pesticide residues on crops and environmental remediation, conducive to the development of SGNH family esterase against pyrethroid accumulation.

Expression, characterization, and immobilization of a novel SGNH esterase Est882 and its potential for pyrethroid degradation

The widely-used pyrethroid pesticides have attracted public attention because of their potentials to cause environmental pollution and toxic effects on non-target organisms. Esterase is a kind of hydrolytic enzyme that can catalyze the cleavage or formation of ester bonds. it plays a pivotal role in the decomposition of pyrethroids and esters containing industrial pollutants through the hydrolysis of ester bonds. Here, a new esterase gene est882 was successfully screened, which encodes Est882, a SGNH family esterase composed of 294 amino acids. It was heterogeneously expressed, identified and immobilized. Multiple sequence alignment showed that Est882 had a typical GDS(X) conserved motif and a catalytic triad composed of Ser79, Asp269 and His275. Phylogenetic analysis showed that Est882 shall belong to a new esterase family. Biochemical characterization demonstrated that the optimum condition was 40°C and pH 9.0. Est882 immobilization was studied with mesoporous silica SBA-15 as the carrier and found to significantly improve the tolerance and stability of Est882. Its optimum pH increased to 10.0 and stabilized within pH 8.0-11.0. Free Est882 can effectively degrade various pyrethroids within 30 min, with a degradation rate above 80%. The immobilized Est882 yet degraded more than 70% of pyrethroids within 30 min. The present study indicated that Est882 has outstanding potential in bioremediation of a pyrethroid-polluted environment. These characteristics endow Est882 with potential values in various industrial applications and hydrolysis of pyrethroid residues.

Is the Mitochondrial Membrane Potential (∆Ψ) Correctly Assessed? Intracellular and Intramitochondrial Modifications of the ∆Ψ Probe, Rhodamine 123

The mitochondrial membrane potential (∆Ψ) is the driving force providing the electrical component of the total transmembrane potential of hydrogen ions generated by proton pumps, which is utilized by the ATP synthase. The role of ∆Ψ is not limited to its role in bioenergetics since it takes part in other important intracellular processes, which leads to the mandatory requirement of the homeostasis of ∆Ψ. Conventionally, ∆Ψ in living cells is estimated by the fluorescence of probes such as rhodamine 123, tetramethylrodamine, etc. However, when assessing the fluorescence, the possibility of the intracellular/intramitochondrial modification of the rhodamine molecule is not taken into account. Such changes were revealed in this work, in which a comparison of normal (astrocytic) and tumor (glioma) cells was conducted. Fluorescent microscopy, flow cytometry, and mass spectrometry revealed significant modifications of rhodamine molecules developing over time, which were prevented by amiodarone apparently due to blocking the release of xenobiotics from the cell and their transformation with the participation of cytochrome P450. Obviously, an important role in these processes is played by the increased retention of rhodamines in tumor cells. Our data require careful evaluation of mitochondrial ∆Ψ potential based on the assessment of the fluorescence of the mitochondrial probe.

Multiple Mechanisms Conferring Broad-Spectrum Insecticide Resistance in the Tropical Bed Bug (Hemiptera: Cimicidae)

The modern resurgence of the common (Cimex lectularius L.) and tropical bed bugs (C. hemipterus [F.]) is thought to be primarily due to insecticide resistance. While there are many reports on insecticide resistance mechanisms in C. lectularius, such information in C. hemipterus is limited. We examined dichloro-diphenyl-trichloroethane (DDT), malathion, deltamethrin, permethrin, lambda-cyhalothrin resistance, and the underlying mechanisms in several C. hemipterus strains (Australia: Queensland [QLD-AU]; Malaysia: Kuala Lumpur [KL-MY], Tanjung Tokong [TT-MY], Christian [CH-MY], and Green Lane [GL-MY]). We used a surface contact method, synergism studies (utilizing piperonyl butoxide [PBO], S,S,S-tributyl phosphorotrithioate [DEF], and diethyl maleate [DEM]), and molecular detection of kdr mutations. Results demonstrated that all C. hemipterus strains possessed high resistance to DDT and the pyrethroids and moderate to high resistance to malathion. Synergism studies showed that deltamethrin resistance in all strains was significantly (P < 0.05) inhibited by PBO. In contrast, deltamethrin resistance was not affected in DEF or DEM. Similar findings were found with lambda-cyhalothrin resistance. Malathion resistance was significantly (P < 0.05) reduced by DEF in all strains. Resistance to DDT was not affected by DEM in all strains. Multiple kdr mutations (M918I, D953G, and L1014F) were detected by molecular analyses. TT-MY strain was found with individuals possessing three kdr mutation combinations; D953G + L1014F (homozygous susceptible: M918), M918I + D953G + L1014F (heterozygous resistant: I918), and M918I + D953G + L1014F (homozygous resistant: I918). Individuals with M918I + D953G + L1014F (homozygous resistant: I918) survived longer on deltamethrin (>12 h) than those (≤1 h) with other combinations. M918I + L1014F mutations most likely conferred super-kdr characteristic toward pyrethroids and DDT in C. hemipterus.

Effect of Fatty Acid Composition in Polysorbate 80 on the Stability of Therapeutic Protein Formulations

Purpose

Polysorbate excipients are commonly used as surfactants to stabilize therapeutic proteins in formulations. Degradation of polysorbates could lead to particle formation and instability of the drug formulation. We investigated how the fatty acid composition of polysorbate 80 impacts the degradation profile, particle formation, and product stability under stress conditions.

Methods

Two polysorbate 80-containing therapeutic protein formulations were reformulated with either Polysorbate 80 NF synthesized from a fatty acid mixture that contains mainly oleic acid (≥58%) or a version of polysorbate 80 synthesized with high oleic acid (>98%). Stress conditions, including high temperature and esterase spiking, were applied and changes to both the polysorbate and the therapeutic protein product were investigated for stability, purity, innate immune response and biological activity.

Results

The addition of esterase and storage at 37°C led to significant hydrolysis of the polysorbate and increases in sub-visible particle formation for both polysorbates tested. The fatty acid composition of polysorbate 80 did not directly alter the stability profile of either therapeutic protein as measured by size exclusion chromatography, or significantly impact innate immune response or biological activity. However, formulations with Polysorbate 80 NF showed greater propensity for sub-visible particle formation under stress conditions.

Conclusions

These results suggest that composition of fatty acids in polysorbate 80 may be a promoter for sub-visible particulate formation under the stress conditions tested but may not impact protein aggregation or biological activity.

Processing of Airborne Green Leaf Volatiles for Their Glycosylation in the Exposed Plants

Green leaf volatiles (GLVs), the common constituents of herbivore-infested plant volatiles (HIPVs), play an important role in plant defense and function as chemical cues to communicate with other individuals in nature. Reportedly, in addition to endogenous GLVs, the absorbance of airborne GLVs emitted by infested neighboring plants also play a major role in plant defense. For example, the exclusive accumulation of (Z)-3-hexenyl vicianoside in the HIPV-exposed tomato plants occurs by the glycosylation of airborne (Z)-3-hexenol (Z3HOL); however, it is unclear how plants process the other absorbed GLVs. This study demonstrates that tomato plants dominantly accumulated GLV-glycosides after exposure to green leaf alcohols [Z3HOL, (E)-2-hexenol, and n-hexanol] using non-targeted LC-MS analysis. Three types of green leaf alcohols were independently glycosylated without isomerization or saturation/desaturation. Airborne green leaf aldehydes and esters were also glycosylated, probably through converting aldehydes and esters into alcohols. Further, we validated these findings in Arabidopsis mutants- (Z)-3-hexenal (Z3HAL) reductase (chr) mutant that inhibits the conversion of Z3HAL to Z3HOL and the acetyl-CoA:(Z)-3-hexen-1-ol acetyltransferase (chat) mutant that impairs the conversion of Z3HOL to (Z)-3-hexenyl acetate. Exposure of the chr and chat mutants to Z3HAL accumulated lower and higher amounts of glycosides than their corresponding wild types (Col-0 and Ler), respectively. These findings suggest that plants process the exogenous GLVs by the reductase(s) and the esterase(s), and a part of the processed GLVs contribute to glycoside accumulation. Overall, the study provides insights into the understanding of the communication of the plants within their ecosystem, which could help develop strategies to protect the crops and maintain a balanced ecosystem.

E2-15

Esterases represent an important class of enzymes with a wide variety of industrial applications. A novel hormone-sensitive lipase (HSL) family esterase, Est19, from the Antarctic bacterium Pseudomonas sp. E2-15 is identified, cloned, and expressed. The enzyme possesses a GESAG motif containing an active serine (S) located within a highly conserved catalytic triad of Ser¹⁵⁵, Asp²⁵³, and His²⁸² residues. The catalytic efficiency (k_cat/K_m) of Est19 for the pNPC6 substrate is 148.68 s^-1mM^-1 at 40 °C. Replacing Glu¹⁵⁴ juxtaposed to the critical catalytic serine with Asp (E154→D substitution) reduced the activity and catalytic efficiency of the enzyme two-fold, with little change in the substrate affinity. The wild-type enzyme retained near complete activity over a temperature range of 10-60 °C, while ~50% of its activity was retained at 0 °C. A phylogenetic analysis suggested that Est19 and its homologs may represent a new subfamily of HSL. The thermal stability and stereo-specificity suggest that the Est19 esterase may be useful for cold and chiral catalyses.

Revisiting Jatropha curcas Monomeric Esterase: A Dienelactone Hydrolase Compatible with the Electrostatic Catapult Model

Jatropha curcas contains seeds with a high oil content, suitable for biodiesel production. After oil extraction, the remaining mass can be a rich source of enzymes. However, data from the literature describing physicochemical characteristics for a monomeric esterase from the J. curcas seed did not fit the electrostatic catapult model for esterases/lipases. We decided to reevaluate this J. curcas esterase and extend its characterization to check this apparent discrepancy and gain insights into the enzyme's potential as a biocatalyst. After anion exchange chromatography and two-dimensional gel electrophoresis, we identified the enzyme as belonging to the dienelactone hydrolase family, characterized by a cysteine as the nucleophile in the catalytic triad. The enzyme displayed a basic optimum hydrolysis pH of 9.0 and an acidic pI range, in contrast to literature data, making it well in line with the electrostatic catapult model. Furthermore, the enzyme showed low hydrolysis activity in an organic solvent-containing medium (isopropanol, acetonitrile, and ethanol), which reverted when recovering in an aqueous reaction mixture. This enzyme can be a valuable tool for hydrolysis reactions of short-chain esters, useful for pharmaceutical intermediates synthesis, due to both its high hydrolytic rate in basic pH and its stability in an organic solvent.