Crystallographic analysis and biochemical applications of a novel penicillin-binding protein/β-lactamase homologue from a metagenomic library

Structural and biochemical characterization of Leptospira interrogans Lsa45 reveals a penicillin-binding protein with esterase activity

Leptospirosis is a bacterial disease that affects humans and animals and is caused by Leptospira. The recommended treatment for leptospirosis is antibiotic therapy, which should be given early in the course of the disease. Despite the use of these antibiotics, their role during the course of the disease is still not completely clear because of the lack of effective clinical trials, particularly for severe cases of the disease. Here, we present the characterization of L. interrogans Lsa45 protein by gel filtration, protein crystallography, SAXS, fluorescence and enzymatic assays. The oligomeric studies revealed that Lsa45 is monomeric in solution. The crystal structure of Lsa45 revealed the presence of two subdomains: a large α/β subdomain and a small α-helical subdomain. The large subdomain contains the amino acids Ser122, Lys125, and Tyr217, which correspond to the catalytic triad that is essential for β-lactamase or serine hydrolase activity in similar enzymes. Additionally, we also confirmed the bifunctional promiscuity of Lsa45, in hydrolyzing both the 4-nitrophenyl acetate (p-NPA) and nitrocefin β-lactam antibiotic. Therefore, this study provides novel insights into the structure and function of enzymes from L. interrogans, which furthers our understanding of this bacterium and the development of new therapies for the prevention and treatment of leptospirosis.

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.

Characterization of a novel thermostable alkaline lipase derived from a compost metagenomic library and its potential application in the detergent industry

Using composted soil samples, a metagenomic library consisting of 36,000 clones was constructed. Then, a novel lipase, Lip54q, which belongs to the VIII family of lipolytic enzymes, was identified from the metagenomic library by functional screening. To explore the enzymatic properties of Lip54q, lip54q was heterologous expressed in Escherichia coli with a high expression level of recombinant protein up to 720 mg/L. The recombinant enzyme showed the highest activity (28,160 U/mg) against a C10 substrate at pH 9.0 and 47°C, and was stable at temperatures ≤50°C and pH 8.0-11.0. Of particular interest, the surfactants, Tween-20, Tween-80 and Tritonx-100, exhibited strong promoting effects on Lip54q activities regardless of whether low concentrations (0.1%) or high concentrations (10%) were used. Application studies of Lip54q using six commercial detergents indicated that the enzyme had strong tolerance and immersion resistance to all six detergents. The results of oil-stain removal experiments suggested that addition of the enzyme to various commercial detergents could significantly improve the abilities of these detergents to remove oil-stains. Furthermore, the results of a molecular docking analysis of Lip54q showed that both the C10 substrate and linoleic acid molecules could form hydrogen bond interactions with the catalytic amino acids, Ser-268, Glu-168, and Asp-192, in the catalytic center of the enzyme, and the hydrogen bond distances were shorter. The electrostatic attraction between the enzyme and the substrate formed by the hydrogen bond with a shorter distance is stronger, which is conducive to the formation of a more stable complex between the enzyme and the substrate, thus increasing the activity of the enzyme to such substrate. These results 1ay a good foundation for application of this enzyme in the detergent industry in the future.

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.

Structural basis for the catalytic activity of filamentous human serine beta-lactamase-like protein LACTB

Serine beta-lactamase-like protein (LACTB) is a mammalian mitochondrial serine protease that can specifically hydrolyze peptide bonds adjacent to aspartic acid residues and is structurally related to prokaryotic penicillin-binding proteins. Here, we determined the cryoelectron microscopy structures of human LACTB (hLACTB) filaments from wild-type protein, a middle region deletion mutant, and in complex with the inhibitor Z-AAD-CMK at 3.0-, 3.1-, and 2.8-Å resolution, respectively. Structural analysis and activity assays revealed that three interfaces are required for the assembly of hLACTB filaments and that the formation of higher order helical structures facilitates its cleavage activity. Further structural and enzymatic analyses of middle region deletion constructs indicated that, while this region is necessary for substrate hydrolysis, it is not required for filament formation. Moreover, the inhibitor-bound structure showed that hLACTB may cleave peptide bonds adjacent to aspartic acid residues. These findings provide the structural basis underlying hLACTB catalytic activity.

Molecular Characterization of Novel Family IV and VIII Esterases from a Compost Metagenomic Library

Two novel esterase genes, est8L and est13L, were isolated and identified from a compost metagenomic library. The encoded Est8L and Est13L had molecular masses of 33,181 and 44,913 Da consisting of 314 and 411 amino acids, respectively, without signal peptides. Est8L showed the highest identity (32.9%) to a hyper-thermophilic carboxylesterase AFEST from Archaeoglobus fulgidus compared to other esterases reported and was classified to be a novel member of family IV esterases with conserved regions such as HGGG, DY, GXSXG, DPL, and GXIH. Est13L showed the highest identity (98.5%) to the family VIII esterase Est7K from the metagenome library. Est8L and Est13L had the highest activities for p-nitrophenyl butyrate (C4) and p-nitrophenyl caproate (C6), respectively, and Est13L showed a broad substrate specificity for p-nitrophenyl substrates. Est8L and Est13L effectively hydrolyzed glyceryl tributyrate. The optimum temperatures for activities of Est8L and Est13L were identical (40 °C), and the optimum pH values were 9.0 and 10.0, respectively. Est13L showed higher thermostability than Est8L. Sephacryl S-200 HR chromatography showed that the native form of Est8L was a dimer. Interestingly, Est13L was found to be a tetramer, contrary to other family VIII esterases reported. Est8L was inhibited by 30% isopropanol, methanol, and acetonitrile; however, Est13L was activated to 182.9% and 356.1%, respectively, by 30% isopropanol and methanol. Est8L showed enantioselectivity for the S-form, but Est13L showed no enantioselectivity. These results show that intracellular Est8L and/or Est13L are oligomeric in terms of native forms and can be used for pharmaceutical and industrial applications with organic solvents under alkaline conditions.

Characterization of a Novel Family IV Esterase Containing a Predicted CzcO Domain and a Family V Esterase with Broad Substrate Specificity from an Oil-Polluted Mud Flat Metagenomic Library

Two novel esterase genes, est2L and est4L, were identified from a previously constructed metagenomic library derived from an oil-polluted mud flat sample. The encoded Est2L and Est4L were composed of 839 and 267 amino acids, respectively, without signal peptides. Est2L was a unique fusion type of protein composed of two domains: a domain of the CzcO superfamily, associated with a cationic diffusion promoter with CzcD, and a domain of the acetylesterase superfamily, belonging to family IV with conserved motifs, such as HGG, GXSAG, and GXPP. Est2L was the first fused esterase with a CzcO domain. Est4L belonged to family V with GXS, GXSMGG, and PTL motifs. Native Est2L and Est4L were found to be in dimeric and tetrameric forms, respectively. Est2L and Est4L showed the highest activities at 60 °C and 50 °C, respectively, and at a pH of 10.0. Est2L preferred short length substrates, especially p-nitrophenyl (pNP)-acetate, with moderate butyrylcholinesterase activity, whereas Est4L showed the highest activity with pNP-decanoate and had broad specificity. Significant effects were not observed in Est2L from Co2+ and Zn2+, although Est2L contains the domain CzcD. Est2L and Est4L showed high stabilities in 30% methanol and 1% Triton X-100. These enzymes could be used for a variety of applications, such as detergent and mining processing under alkaline conditions.

Characterization of a novel carboxylesterase belonging to family VIII hydrolyzing β-lactam antibiotics from a compost metagenomic library

A novel esterase, EstCS3, was isolated from a metagenomic library constructed from a compost. The EstCS3, which consists of 409 amino acids with an anticipated molecular mass of 44 kDa, showed high amino acid sequence identities to predicted esterases, serine hydrolases and β-lactamases from uncultured and cultured bacteria. Phylogenetic analysis suggested that EstCS3 belongs to family VIII of lipolytic enzymes. EstCS3 had catalytic Ser78 residue in the consensus tetrapeptide motif SXXK, which is characteristic of family VIII esterases. Two conserved YXX and W(H or K)XG motifs in an oxyanion hole of family VIII esterases were also present in EstCS3. EstCS3 demonstrated the highest activity toward p-nitrophenyl butyrate (C4) and was stable up to 70 °C with optimal activity at 55 °C. EstCS3 had optimal activity at pH 8 and maintained its stability within pH range of 7-10. EstCS3 had over 70% activity in the presence of 20% (v/v) methanol and DMSO and hydrolyzed sterically hindered tertiary alcohol esters of t-butyl acetate and linalyl acetate. EstCS3 hydrolyzed ampicillin, cephalothin and cefepime. The properties of EstCS3, including moderate thermostability, stability against organic solvents and activity toward esters of tertiary alcohols, indicated that it has the potential to be used in industrial applications.

Characterization of a Novel Moderately Thermophilic Solvent-Tolerant Esterase Isolated From a Compost Metagenome Library

A novel esterase, EstCS1, was isolated from a compost metagenomics library. The EstCS1 protein, which consists of 309 amino acid residues with an anticipated molecular mass of 34 kDa, showed high amino acid sequence identities to predicted esterases and alpha/beta hydrolases (59%) from some cultured bacteria and to predicted lipases/esterases from uncultured bacteria. The phylogenetic analysis suggested that the EstCS1 belongs to the hormone-sensitive lipase family of lipolytic enzyme classification and contains a catalytic triad including Ser155–Asp255–His285. The Ser155 residue of the catalytic triad in the EstCS1 was located in the consensus active-site motif, GXSXG. Besides, a conserved HGGG motif placed in an oxyanion hole of the hormone-sensitive lipase family was discovered, too. The EstCS1 demonstrated the highest activity toward p-nitrophenyl propionate (C3) and caproate (C6) and was normally stable up to 60°C with optimal activity at 50°C. In addition, an optimal activity was observed at pH 8, and the EstCS1 possessed its stability within the pH range between 5 and 10. Interestingly, EstCS1 had an outstanding stability in up to 30% (v/v) organic solvents and activity over 50% in the presence of 50% (v/v) acetone, ethanol, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide. The EstCS1 hydrolyzed sterically hindered tertiary alcohol esters of t-butyl acetate and linalyl acetate. Considering the properties, such as the moderate thermostability, stability against organic solvents, and activity toward esters of tertiary alcohols, the EstCS1 will be worthwhile to be used for organic synthesis and related industrial applications.

Molecular Characterization of a Novel Family VIII Esterase with β-Lactamase Activity (PsEstA) from Paenibacillus sp

Molecular information about family VIII esterases, which have similarities with class C β-lactamases and penicillin-binding proteins, remains largely unknown. In this study, a novel family VIII esterase with β-lactamase activity (PsEstA) from Paenibacillus sp. was characterized using several biochemical and biophysical methods. PsEstA was effective on a broad range of substrates including tertiary butyl acetate, glyceryl tributyrate, glucose pentaacetate, olive oil, and p-nitrophenyl esters. Additionally, PsEstA hydrolyzed nitrocefin, cefotaxime, and 7-aminocephalosporanic acid. Interestingly, two forms of immobilized PsEstA (CLEAs-PsEstA and mCLEAs-PsEstA) showed high recycling property and enhanced stability, but hybrid nanoflowers (hNFs) of PsEstA require improvement. This study provides a molecular understanding of substrate specificities, catalytic regulation, and immobilization of PsEstA, which can be efficiently used in biotechnological applications.

A Novel VIII Carboxylesterase with High Hydrolytic Activity Against Ampicillin from a Soil Metagenomic Library

A novel carboxylesterase gene, named dlfae4, was discovered and sequenced from a soil metagenomic library. The dlfae4 gene was composed of 1017 base pairs encoding 338 amino acid residues with a predicted molecular mass of 37.2 kDa. DLFae4 exhibited strong hydrolytic activity towards methyl ferulate under optimum pH and temperature conditions (pH 8.6, 50 °C) and displayed remarkable thermostability, with residual activity as high as 50% after incubation for 3 h at 60 °C. A family VIII esterase DLFae4 was found to contain a typical serine residue within the S-X-X-K motif, which serves as a catalytic nucleophile in class C β-lactamases and family VIII esterases. As a consequence of its high sequence similarity with β-lactamases, DLFae4 exhibited significant hydrolytic activity towards ampicillin. In addition, DLFae4 was found to be the first known member of family VIII carboxylesterases with phthalate-degrading ability. Site-directed mutagenesis studies revealed that Ser11, Lys14, and Tyr121 residues play an essential catalytic role in DLFae4. These new findings, which are of great importance for further in-depth research and engineering development of carboxylesterases, should advance the implementation of biotechnological applications.

Biochemical profiles of two thermostable and organic solvent-tolerant esterases derived from a compost metagenome

Owing to the functional versatility and potential applications in industry, interest in lipolytic enzymes tolerant to organic solvents is increasing. In this study, functional screening of a compost soil metagenome resulted in identification of two lipolytic genes, est1 and est2, encoding 270 and 389 amino acids, respectively. The two genes were heterologously expressed and characterized. Est1 and Est2 are thermostable enzymes with optimal enzyme activities at 80 and 70 °C, respectively. A second-order rotatable design, which allows establishing the relationship between multiple variables with the obtained responses, was used to explore the combined effects of temperature and pH on esterase stability. The response curve indicated that Est1, and particularly Est2, retained high stability within a broad range of temperature and pH values. Furthermore, the effects of organic solvents on Est1 and Est2 activities and stabilities were assessed. Notably, Est2 activity was significantly enhanced (two- to tenfold) in the presence of ethanol, methanol, isopropanol, and 1-propanol over a concentration range between 6 and 30% (v/v). For the short-term stability (2 h of incubation), Est2 exhibited high tolerance against 60% (v/v) of ethanol, methanol, isopropanol, DMSO, and acetone, while Est1 activity resisted these solvents only at lower concentrations (below 30%, v/v). Est2 also displayed high stability towards some water-immiscible organic solvents, such as ethyl acetate, diethyl ether, and toluene. With respect to long-term stability, Est2 retained most of its activity after 26 days of incubation in the presence of 30% (v/v) ethanol, methanol, isopropanol, DMSO, or acetone. All of these features indicate that Est1 and Est2 possess application potential.

Relationships between Substrate Promiscuity and Chiral Selectivity of Esterases from Phylogenetically and Environmentally Diverse Microorganisms

Substrate specificity and selectivity of a biocatalyst are determined by the protein sequence and structure of its active site. Finding versatile biocatalysts acting against multiple substrates while at the same time being chiral selective is of interest for the pharmaceutical and chemical industry. However, the relationships between these two properties in natural microbial enzymes remain underexplored. Here, we performed an experimental analysis of substrate promiscuity and chiral selectivity in a set of 145 purified esterases from phylogenetically and environmentally diverse microorganisms, which were assayed against 96 diverse esters, 20 of which were enantiomers. Our results revealed a negative correlation between substrate promiscuity and chiral selectivity in the evaluated enzymes. Esterases displaying prominent substrate promiscuity and large catalytic environments are characterized by low chiral selectivity, a feature that has limited commercial value. Although a low level of substrate promiscuity does not guarantee high chiral selectivity, the probability that esterases with smaller active sites possess chiral selectivity factors of interest for industry (>25) is significantly higher than for promiscuous enzymes. Together, the present study unambiguously demonstrates that promiscuous and selective esterases appear to be rare in nature and that substrate promiscuity can be used as an indicator of the chiral selectivity level of esterases, and vice versa.

Identification, characterization, immobilization, and mutational analysis of a novel acetylesterase with industrial potential (LaAcE) from Lactobacillus acidophilus

Lactic acid bacteria, which are involved in the fermentation of vegetables, meats, and dairy products, are widely used for the productions of small organic molecules and bioactive peptides. Here, a novel acetylesterase (LaAcE) from Lactobacillus acidophilus NCFM was identified, functionally characterized, immobilized, and subjected to site-directed mutagenesis for biotechnological applications. The enzymatic properties of LaAcE were investigated using biochemical and biophysical methods including native polyacrylamide gel electrophoresis, acetic acid release, biochemical assays, enzyme kinetics, and spectroscopic methods. Interestingly, LaAcE exhibited the ability to act on a broad range of substrates including glucose pentaacetate, glyceryl tributyrate, fish oil, and fermentation-related compounds. Furthermore, immobilization of LaAcE showed good recycling ability and high thermal stability compared with free LaAcE. A structural model of LaAcE was used to guide mutational analysis of hydrophobic substrate-binding region, which was composed of Leu¹⁵⁶, Phe¹⁶⁴, and Val²⁰⁴. Five mutants (L156A, F164A, V204A, L156A/F164A, and L156A/V204A) were generated and investigated to elucidate the roles of these hydrophobic residues in substrate specificity. This work provided valuable insights into the properties of LaAcE, and demonstrated that LaAcE could be used as a model enzyme of acetylesterase in lactic acid bacteria, making LaAcE a great candidate for industrial applications.

Characterization of a novel SGNH-type esterase from Lactobacillus plantarum

Lactic acid bacteria (LAB) are sources of a large variety of microbial ester hydrolases because they can produce a wide range of short-chain esters, phenolic alcohols, and fatty acids. Here, a novel SGNH-type esterase (LpSGNH1) from Lactobacillus plantarum WCFS1 was identified, functionally characterized, and immobilized for biotechnological applications. Homologs of LpSGNH1 are also found in many lactic acid bacteria (LAB) species. Biochemical features of LpSGNH1 were investigated using mass spectrometry, gel filtration chromatography, enzyme kinetics, fluorescence, and circular dichroism (CD) spectroscopy. LpSGNH1 were retained its activity under conditions that would be encountered during fermentations. Interestingly, LpSGNH1 exhibited the ability to act on a broad range of substrates including ketoprofen acetate, cefotaxime (CTX), and 7-aminocephalosporanic acid (7-ACA) as well as glucose pentaacetate, acetylxylan, and acetylalginate, which make LpSGNH1 a great candidate for extensive industrial applications. Furthermore, cross-linked enzyme aggregates of LpSGNH1 (CLEA-LpSGNH1) displayed recycling ability and thermal stability compared to free LpSGNH1, which could be useful for industrial applications. This work highlights the importance of LpSGNH1 in the preparation of commercial compounds, and LpSGNH1 can be used as a model system of SGNH esterases in lactic acid bacteria.

Biochemical and Structural Analysis of a Novel Esterase from Caulobacter crescentus related to Penicillin-Binding Protein (PBP)

Considering that the prevalence of antibiotic-resistant pathogenic bacteria is largely increasing, a thorough understanding of penicillin-binding proteins (PBPs) is of great importance and crucial significance because this enzyme family is a main target of β-lactam-based antibiotics. In this work, combining biochemical and structural analysis, we present new findings that provide novel insights into PBPs. Here, a novel PBP homologue (CcEstA) from Caulobacter crescentus CB15 was characterized using native-PAGE, mass spectrometry, gel filtration, CD spectroscopy, fluorescence, reaction kinetics, and enzyme assays toward various substrates including nitrocefin. Furthermore, the crystal structure of CcEstA was determined at a 1.9 Å resolution. Structural analyses showed that CcEstA has two domains: a large α/β domain and a small α-helix domain. A nucleophilic serine (Ser⁶⁸) residue is located in a hydrophobic groove between the two domains along with other catalytic residues (Lys⁷¹ and Try¹⁵⁷). Two large flexible loops (UL and LL) of CcEstA are proposed to be involved in the binding of incoming substrates. In conclusion, CcEstA could be described as a paralog of the group that contains PBPs and β-lactamases. Therefore, this study could provide new structural and functional insights into the understanding this protein family.

Structural and Biochemical Characterization of an Octameric Carbohydrate Acetylesterase from Sinorhizobium meliloti

Carbohydrate acetylesterases, which have a highly specific role among plant-interacting bacterial species, remove the acetyl groups from plant carbohydrates. Here, we determined the crystal structure of Est24, an octameric carbohydrate acetylesterase from Sinorhizobium meliloti, at 1.45 Å resolution and investigated its biochemical properties. The structure of Est24 consisted of five parallel β strands flanked by α helices, which formed an octameric assembly with two distinct interfaces. The deacetylation activity of Est24 and its mutants around the substrate-binding pocket was investigated using several substrates, including glucose pentaacetate and acetyl alginate. Elucidation of the structure-function relationships of Est24 could provide valuable opportunities for biotechnological explorations.

Structural and biochemical characterization of a carbohydrate acetylesterase from Sinorhizobium meliloti 1021

In many microorganisms, carbohydrate acetylesterases remove the acetyl groups from various types of carbohydrates. Sm23 from Sinorhizobium meliloti is a putative member of carbohydrate esterase family 3 (CE3) in the CAZy classification system. Here, we determined the crystal structure of Sm23 at 1.75 Å resolution and investigated functional properties using biochemical methods. Furthermore, immobilized Sm23 exhibited improved stability compared with soluble Sm23, which can be used for the design of plant cell wall degrading-systems.

Identification, characterization, and immobilization of an organic solvent-stable alkaline hydrolase (PA27) from Pseudomonas aeruginosa MH38

An organic solvent-stable alkaline hydrolase (PA27) from Pseudomonas aeruginosa MH38 was expressed, characterized, and immobilized for biotechnological applications. Recombinant PA27 was expressed in Escherichia coli as a 27 kDa soluble protein and was purified by standard procedures. PA27 was found to be stable at pH 8–11 and below 50 °C. It maintained more than 80% of its activity under alkaline conditions (pH 8.0–11.0). Furthermore, PA27 exhibited remarkable stability in benzene and n-hexane at concentrations of 30% and 50%. Based on these properties, immobilization of PA27 for biotechnological applications was explored. Scanning electron microscopy revealed a very smooth spherical structure with numerous large pores. Interestingly, immobilized PA27 displayed improved thermal/chemical stabilities and high reusability. Specifically, immobilized PA27 has improved thermal stability, maintaining over 90% of initial activity after 1 h of incubation at 80 °C, whereas free PA27 had only 35% residual activity. Furthermore, immobilized PA27 showed higher residual activity than the free enzyme biocatalysts against detergents, urea, and phenol. Immobilized PA27 could be recycled 20 times with retention of ~60% of its initial activity. Furthermore, macroscopic hydrogel formation of PA27 was also investigated. These characteristics make PA27 a great candidate for an industrial biocatalyst with potential applications.