RESUMEN

Lectins are carbohydrate-binding proteins belonging to the Leguminosae family. In this family stand out proteins extracted from species belonging to Diocleinae subtribe, which includes, for example, the seed lectin from Dioclea violacea (DVL) and the jack bean lectin Concanavalin A (ConA). Here, we report the photosynthesis of silver/silver chloride nanoparticles (NPs) assisted by ConA and DVL. The syntheses were simple processes using a green-chemistry approach. Under electron microscopy, NPs heterogeneous in size, nearly spherical and covered by a thin lectin corona, were observed. Both NPs assisted by lectins were capable to cause strong rabbit erythrocytes agglutination with the same titers of hemagglutinating activities. These results indicate that both lectins maintained their biological activities even after association with the NPs and therefore are able to interact with biological membrane carbohydrates. However, for rabbit erythrocytes treated with proteolytic enzymes were observed different titers of hemagglutinating activities, suggesting differences in the spatial arrangement of the lectins on the surface of the NPs. This study provides evidences that these hybrid lectin-coated silver/silver chloride NPs can be used for selective recognition and interaction with membrane carbohydrates and others biotechnological applications.

Asunto(s)

Lectinas , Lectinas de Plantas , Animales , Conejos , Lectinas/química , Lectinas de Plantas/farmacología , Lectinas de Plantas/química , Lectinas de Plantas/metabolismo , Plata/farmacología , Carbohidratos/química , Fotosíntesis

RESUMEN

The ferulic acid (FA) represents a high-value molecule with applications in the cosmetic and pharmaceutical industries. This aromatic molecule is derived from lignin and can be enzymatically converted in other commercially interesting molecules, such as vanillin and bioplastics. This process starts with a common step of FA activation via CoA-thioesterification, catalyzed by feruloyl-CoA synthetases. Therefore, here, we report the successfully expression, purification as well as the initial structural and biochemical characterization of a stable, correctly folded, and catalytically active bacterial feruloyl-CoA synthase (here named FCS3) isolated from a lignin-degrading microbial consortium. The purification of recombinant FCS3 to near homogeneity was achieved using affinity chromatography. The FCS3 structure is composed of a mixture of α and ß secondary structures and most likely forms stable homodimers in solution. The FCS3 presented a notable structural stability at alkaline pH values and it was able to convert FA and coenzyme A (CoA) into feruloyl-CoA complex at room temperature. This study should provide a useful basis for future biotechnological applications of FCS3, especially in the field of conversion of lignin-derived FA into high value compounds.

Asunto(s)

Benzaldehídos , Lignina , Acilcoenzima A/metabolismo , Benzaldehídos/metabolismo , Ácidos Cumáricos/metabolismo , Lignina/metabolismo

RESUMEN

Aim: Two lytic phages were isolated using P. aeruginosa DSM19880 as host and fully characterized. Materials & methods: Phages were characterized physicochemically, biologically and genomically. Results & conclusion: Host range analysis revealed that the phages also infect some multidrug-resistant (MDR) P. aeruginosa clinical isolates. Increasing MOI from 1 to 1000 significantly increased phage efficiency and retarded bacteria regrowth, but phage ph0034 (reduction of 7.5 log CFU/ml) was more effective than phage ph0031 (reduction of 5.1 log CFU/ml) after 24 h. Both phages belong to Myoviridae family. Genome sequencing of phages ph0031 and ph0034 showed that they do not carry toxin, virulence, antibiotic resistance and integrase genes. The results obtained are highly relevant in the actual context of bacterial resistance to antibiotics.

Asunto(s)

Bacteriófagos , Pseudomonas aeruginosa , Bacteriófagos/genética , Especificidad del Huésped , Técnicas In Vitro , Myoviridae/genética

RESUMEN

Saliva is a biofluid that maintains the health of oral tissues and the homeostasis of oral microbiota. Studies have demonstrated that Oral squamous cell carcinoma (OSCC) patients have different salivary microbiota than healthy individuals. However, the relationship between these microbial differences and clinicopathological outcomes is still far from conclusive. Herein, we investigate the capability of using metagenomic and metaproteomic saliva profiles to distinguish between Control (C), OSCC without active lesion (L0), and OSCC with active lesion (L1) patients. The results show that there are significantly distinct taxonomies and functional changes in L1 patients compared to C and L0 patients, suggesting compositional modulation of the oral microbiome, as the relative abundances of Centipeda, Veillonella, and Gemella suggested by metagenomics are correlated with tumor size, clinical stage, and active lesion. Metagenomics results also demonstrated that poor overall patient survival is associated with a higher relative abundance of Stenophotromonas, Staphylococcus, Centipeda, Selenomonas, Alloscordovia, and Acitenobacter. Finally, compositional and functional differences in the saliva content by metaproteomics analysis can distinguish healthy individuals from OSCC patients. In summary, our study suggests that oral microbiota and their protein abundance have potential diagnosis and prognosis value for oral cancer patients. Further studies are necessary to understand the role of uniquely detected metaproteins in the microbiota of healthy and OSCC patients as well as the crosstalk between saliva host proteins and the oral microbiome present in OSCC.

Asunto(s)

Saliva/microbiología , Carcinoma de Células Escamosas de Cabeza y Cuello/microbiología , Adulto , Anciano , Estudios de Cohortes , Femenino , Humanos , Masculino , Metagenómica/métodos , Microbiota/genética , Persona de Mediana Edad , Neoplasias de la Boca/metabolismo , Neoplasias de la Boca/microbiología , Pronóstico , Proteómica/métodos , Carcinoma de Células Escamosas de Cabeza y Cuello/metabolismo

RESUMEN

It is urgent the transition from a fossil fuel-based economy to a sustainable bioeconomy based on bioconversion technologies using renewable plant biomass feedstocks to produce high chemicals, bioplastics, and biofuels. ß-Glucosidases are key enzymes responsible for degrading the plant cell wall polymers, as they cleave glucan-based oligo- and polysaccharides to generate glucose. Monosaccharide-tolerant or -stimulated ß-glucosidases have been reported in the past decade. Here, we describe a novel mechanism of ß-glucosidase stimulation by glucose and xylose. The glycoside hydrolase 1 family ß-glucosidase from Thermotoga petrophila (TpBgl1) displays a typical glucose stimulation mechanism based on an increased Vmax and decreased Km in response to glucose. Through molecular docking and dynamics analyses, we mapped putative monosaccharide binding regions (BRs) on the surface of TpBgl1. Our results indicate that after interaction with glucose or xylose at BR1 site, an adjacent loop region assumes an extended conformation, which increases the entrance to the TpBgl1 active site, improving product formation. Biochemical assays with TpBgl1 BR1 mutants, TpBgl1D49A/Y410A and TpBgl1D49K/Y410H, resulted in decreasing and abolishing monosaccharide stimulation, respectively. These mutations also impaired the BR1 looping extension responsible for monosaccharide stimulation. This study provides a molecular basis for the rational design of ß-glucosidases for biotechnological applications.

Asunto(s)

Monosacáridos/metabolismo , Thermotoga/enzimología , beta-Glucosidasa/química , beta-Glucosidasa/metabolismo , Biocatálisis , Dominio Catalítico , Glucosa/metabolismo , Cinética , Simulación de Dinámica Molecular , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Unión Proteica , Conformación Proteica , Xilosa/metabolismo

RESUMEN

Lignocellulose is one of the most abundant renewable carbon sources, representing an alternative to petroleum for the production of fuel and chemicals. Nonetheless, the lignocellulose saccharification process, to release sugars for downstream applications, is one of the most crucial factors economically challenging to its use. The synergism required among the various carbohydrate-active enzymes (CAZymes) for efficient lignocellulose breakdown is often not satisfactorily achieved with an enzyme mixture from a single strain. To overcome this challenge, enrichment strategies can be applied to develop microbial communities with an efficient CAZyme arsenal, incorporating complementary and synergistic properties, to improve lignocellulose deconstruction. We report a comprehensive and deep analysis of an enriched rumen anaerobic consortium (ERAC) established on sugarcane bagasse (SB). The lignocellulolytic abilities of the ERAC were confirmed by analyzing the depolymerization of bagasse by scanning electron microscopy, enzymatic assays, and mass spectrometry. Taxonomic analysis based on 16S rRNA sequencing elucidated the community enrichment process, which was marked by a higher abundance of Firmicutes and Synergistetes species. Shotgun metagenomic sequencing of the ERAC disclosed 41 metagenome-assembled genomes (MAGs) harboring cellulosomes and polysaccharide utilization loci (PULs), along with a high diversity of CAZymes. The amino acid sequences of the majority of the predicted CAZymes (60% of the total) shared less than 90% identity with the sequences found in public databases. Additionally, a clostridial MAG identified in this study produced proteins during consortium development with scaffoldin domains and CAZymes appended to dockerin modules, thus representing a novel cellulosome-producing microorganism.IMPORTANCE The lignocellulolytic ERAC displays a unique set of plant polysaccharide-degrading enzymes (with multimodular characteristics), cellulosomal complexes, and PULs. The MAGs described here represent an expansion of the genetic content of rumen bacterial genomes dedicated to plant polysaccharide degradation, therefore providing a valuable resource for the development of biocatalytic toolbox strategies to be applied to lignocellulose-based biorefineries.

Asunto(s)

Bacterias Anaerobias/metabolismo , Proteínas Bacterianas/metabolismo , Celulosomas/metabolismo , Microbioma Gastrointestinal , Lignina/metabolismo , Consorcios Microbianos , Polisacáridos/metabolismo , Animales , Bacterias Anaerobias/enzimología , Celulasas/metabolismo , Celulosa , Rumen/microbiología , Saccharum

RESUMEN

Wickerhamomyces anomalus LBCM1105 is a yeast isolated from cachaça distillery fermentation vats, notable for exceptional glycerol consumption ability. We report its draft genome with 20.5x in-depth coverage and around 90% extension and completeness. It harbors the sequences of proteins involved in glycerol transport and metabolism.

RESUMEN

The repertoire of redox-active enzymes produced by the marine fungus Peniophora sp. CBMAI 1063, a laccase hyper-producer strain, was characterized by omics analyses. The genome revealed 309 Carbohydrate-Active Enzymes (CAZymes) genes, including 48 predicted genes related to the modification and degradation of lignin, whith 303 being transcribed under cultivation in optimized saline conditions for laccase production. The secretome confirmed that the fungus can produce a versatile ligninolytic enzyme cocktail. It secretes 56 CAZymes, including 11 oxidative enzymes classified as members of auxiliary activity families (AAs), comprising two laccases, Pnh_Lac1 and Pnh_Lac2, the first is the major secretory protein of the fungi. The Pnh_Lac1-mediator system was able to promote the depolymerization of lignin fragments and polymeric lignin removal from pretreated sugarcane bagasse, confirming viability of this fungus enzymatic system for lignocellulose-based bioproducts applications.

Asunto(s)

Basidiomycota/enzimología , Lacasa/metabolismo , Lignina/metabolismo , Oxidación-Reducción , Basidiomycota/genética , Basidiomycota/metabolismo , ADN de Hongos/genética , Genes Fúngicos/genética , Genoma Fúngico/genética , Filogenia

RESUMEN

Secretome evaluations of lignocellulose-decay basidiomycetes can reveal new enzymes in selected fungal species that degrade specific substrates. Proteins discovered in such studies can support biorefinery development. Brown-rot (Gloeophyllum trabeum) and white-rot (Pleurotus ostreatus) fungi growing in sugarcane bagasse solid-state cultures produced 119 and 63 different extracellular proteins, respectively. Several of the identified enzymes are suitable for in vitro biomass conversion, including a range of cellulases (endoglucanases, cellobiohydrolases and ß-glucosidases), hemicellulases (endoxylanases, α-arabinofuranosidases, α-glucuronidases and acetylxylan esterases) and carbohydrate-active auxiliary proteins, such as AA9 lytic polysaccharide monooxygenase, AA1 laccase and AA2 versatile peroxidase. Extracellular oxalate decarboxylase was also detected in both fungal species, exclusively in media containing sugarcane bagasse. Interestingly, intracellular AA6 quinone oxidoreductases were also exclusively produced under sugarcane bagasse induction in both fungi. These enzymes promote quinone redox cycling, which is used to produce Fenton's reagents by lignocellulose-decay fungi. Hitherto undiscovered hypothetical proteins that are predicted in lignocellulose-decay fungi genomes appeared in high relative abundance in the cultures containing sugarcane bagasse, which suggests undisclosed, new biochemical mechanisms that are used by lignocellulose-decay fungi to degrade sugarcane biomass. In general, lignocellulose-decay fungi produce a number of canonical hydrolases, as well as some newly observed enzymes, that are suitable for in vitro biomass digestion in a biorefinery context.

Asunto(s)

Basidiomycota/metabolismo , Celulosa/metabolismo , Lignina/metabolismo , Metaboloma , Pleurotus/metabolismo , Saccharum/metabolismo , Biomasa , Celulasas/metabolismo , Celulosa 1,4-beta-Celobiosidasa/metabolismo , Proteínas Fúngicas/metabolismo , Glucosa/metabolismo , Madera/metabolismo , Madera/microbiología

RESUMEN

Cellulases are essential enzymatic components for the transformation of plant biomass into fuels, renewable materials and green chemicals. Here, we determined the crystal structure, pattern of hydrolysis products release, and conducted molecular dynamics simulations of the major endoglucanase from the Xanthomonas campestris pv. campestris (XccCel5A). XccCel5A has a TIM barrel fold with the catalytic site centrally placed in a binding groove surrounded by aromatic side chains. Molecular dynamics simulations show that productive position of the substrate is secured by a network of hydrogen bonds in the four main subsites, which differ in details from homologous structures. Capillary zone electrophoresis and computational studies reveal XccCel5A can act both as endoglucanase and licheninase, but there are preferable arrangements of substrate regarding ß-1,3 and ß-1,4 bonds within the binding cleft which are related to the enzymatic efficiency.

Asunto(s)

Celulasa/química , Celulasa/metabolismo , Simulación de Dinámica Molecular , Oligosacáridos/metabolismo , Xanthomonas campestris/enzimología , Dominio Catalítico , Cristalografía por Rayos X , Hidrólisis

RESUMEN

We report here the draft genome sequence of Lysinibacillus sphaericus strain A1, a potential lignin-degrading bacterium isolated from municipal solid waste (MSW) soil and capable of enhancing gas release from lignocellulose-containing soil.

RESUMEN

Laccase production in saline conditions is still poorly studied. The aim of the present study was to investigate the production of laccase in two different types of bioreactors by the marine-derived basidiomycete Peniophora sp. CBMAI 1063. The highest laccase activity and productivity were obtained in the Stirred Tank (ST) bioreactor, while the highest biomass concentration in Air-lift (AL) bioreactor. The main laccase produced was purified by ion exchange and size exclusion chromatography and appeared to be monomeric with molecular weight of approximately 55 kDa. The optimum oxidation activity was obtained at pH 5.0. The thermal stability of the enzyme ranged from 30 to 50 °C (120 min). The Far-UV Circular Dichroism revealed the presence of high ß-sheet and low α-helical conformation in the protein structure. Additional experiments carried out in flask scale showed that the marine-derived fungus was able to produce laccase only in the presence of artificial seawater and copper sulfate. Results from the present study confirmed the fungal adaptation to marine conditions and its potential for being used in saline environments and/or processes.

Asunto(s)

Organismos Acuáticos/metabolismo , Basidiomycota/metabolismo , Reactores Biológicos/microbiología , Medios de Cultivo/química , Lacasa/metabolismo , Solución Salina/metabolismo , Organismos Acuáticos/crecimiento & desarrollo , Basidiomycota/crecimiento & desarrollo , Cromatografía en Gel , Cromatografía por Intercambio Iónico , Dicroismo Circular , Sulfato de Cobre/metabolismo , Estabilidad de Enzimas , Concentración de Iones de Hidrógeno , Lacasa/química , Lacasa/aislamiento & purificación , Peso Molecular , Oxidación-Reducción , Estructura Secundaria de Proteína , Temperatura

RESUMEN

BACKGROUND: Lignin is a heterogeneous polymer representing a renewable source of aromatic and phenolic bio-derived products for the chemical industry. However, the inherent structural complexity and recalcitrance of lignin makes its conversion into valuable chemicals a challenge. Natural microbial communities produce biocatalysts derived from a large number of microorganisms, including those considered unculturable, which operate synergistically to perform a variety of bioconversion processes. Thus, metagenomic approaches are a powerful tool to reveal novel optimized metabolic pathways for lignin conversion and valorization. RESULTS: The lignin-degrading consortium (LigMet) was obtained from a sugarcane plantation soil sample. The LigMet taxonomical analyses (based on 16S rRNA) indicated prevalence of Proteobacteria, Actinobacteria and Firmicutes members, including the Alcaligenaceae and Micrococcaceae families, which were enriched in the LigMet compared to sugarcane soil. Analysis of global DNA sequencing revealed around 240,000 gene models, and 65 draft bacterial genomes were predicted. Along with depicting several peroxidases, dye-decolorizing peroxidases, laccases, carbohydrate esterases, and lignocellulosic auxiliary (redox) activities, the major pathways related to aromatic degradation were identified, including benzoate (or methylbenzoate) degradation to catechol (or methylcatechol), catechol ortho-cleavage, catechol meta-cleavage, and phthalate degradation. A novel Paenarthrobacter strain harboring eight gene clusters related to aromatic degradation was isolated from LigMet and was able to grow on lignin as major carbon source. Furthermore, a recombinant pathway for vanillin production was designed based on novel gene sequences coding for a feruloyl-CoA synthetase and an enoyl-CoA hydratase/aldolase retrieved from the metagenomic data set. CONCLUSION: The enrichment protocol described in the present study was successful for a microbial consortium establishment towards the lignin and aromatic metabolism, providing pathways and enzyme sets for synthetic biology engineering approaches. This work represents a pioneering study on lignin conversion and valorization strategies based on metagenomics, revealing several novel lignin conversion enzymes, aromatic-degrading bacterial genomes, and a novel bacterial strain of potential biotechnological interest. The validation of a biosynthetic route for vanillin synthesis confirmed the applicability of the targeted metagenome discovery approach for lignin valorization strategies.

RESUMEN

Feruloylation of arabinoxylan (AX) in grass cell walls is a key determinant of recalcitrance to enzyme attack, making it a target for improvement of grass crops, and of interest in grass evolution. Definitive evidence on the genes responsible is lacking so we studied a candidate gene that we identified within the BAHD acyl-CoA transferase family. We used RNA interference (RNAi) silencing of orthologs in the model grasses Setaria viridis (SvBAHD01) and Brachypodium distachyon (BdBAHD01) and determined effects on AX feruloylation. Silencing of SvBAHD01 in Setaria resulted in a c. 60% decrease in AX feruloylation in stems consistently across four generations. Silencing of BdBAHD01 in Brachypodium stems decreased feruloylation much less, possibly due to higher expression of functionally redundant genes. Setaria SvBAHD01 RNAi plants showed: no decrease in total lignin, approximately doubled arabinose acylated by p-coumarate, changes in two-dimensional NMR spectra of unfractionated cell walls consistent with biochemical estimates, no effect on total biomass production and an increase in biomass saccharification efficiency of 40-60%. We provide the first strong evidence for a key role of the BAHD01 gene in AX feruloylation and demonstrate that it is a promising target for improvement of grass crops for biofuel, biorefining and animal nutrition applications.

Asunto(s)

Biomasa , Pared Celular/metabolismo , Coenzima A Transferasas/genética , Ácidos Cumáricos/metabolismo , Genes de Plantas , Setaria (Planta)/enzimología , Setaria (Planta)/genética , Supresión Genética , Ácidos/metabolismo , Brachypodium/genética , Metabolismo de los Hidratos de Carbono , Coenzima A Transferasas/metabolismo , Regulación de la Expresión Génica de las Plantas , Silenciador del Gen , Hidrólisis , Lignina/metabolismo , Espectroscopía de Resonancia Magnética , Tamaño de los Órganos , Filogenia , Tallos de la Planta/metabolismo , Plantas Modificadas Genéticamente , Semillas/anatomía & histología , Semillas/crecimiento & desarrollo , Transcriptoma/genética , Xilanos/metabolismo

RESUMEN

Lignin is a major obstacle for cost-effective conversion of cellulose into fermentable sugars. Non-productive adsorption onto insoluble lignin fragments and interactions with soluble phenols are important inhibition mechanisms of cellulases, including ß-glucosidases. Here, we examined the inhibitory effect of tannic acid (TAN), a model polyphenolic compound, on ß-glucosidases from the bacterium Thermotoga petrophila (TpBGL1 and TpBGL3) and archaeon Pyrococcus furiosus (PfBGL1). The results revealed that the inhibition effects on ß-glucosidases were TAN concentration-dependent. TpBGL1 and TpBGL3 were more tolerant to the presence of TAN when compared with PfBGL1, while TpBGL1 was less inhibited when compared with TpBGL3. In an attempt to better understand the inhibitory effect, the interaction between TAN and ß-glucosidases were analyzed by isothermal titration calorimetry (ITC). Furthermore, the exposed hydrophobic surface areas in ß-glucosidases were analyzed using a fluorescent probe and compared with the results of inhibition and ITC. The binding constants determined by ITC for the interactions between TAN and ß-glucosidases presented the same order of magnitude. However, the number of binding sites and exposed hydrophobic surface areas varied for the ß-glucosidases studied. The binding between TAN and ß-glucosidases were driven by enthalpic effects and with an unfavorable negative change in entropy upon binding. Furthermore, the data suggest that there is a high correlation between exposed hydrophobic surface areas and the number of binding sites on the inhibition of microbial ß-glucosidases by TAN. These studies can be useful for biotechnological applications.

Asunto(s)

Inhibidores Enzimáticos/farmacología , Bacilos Gramnegativos Anaerobios Rectos, Curvos y Espirales/enzimología , Pyrococcus furiosus/enzimología , Taninos/farmacología , beta-Glucosidasa/metabolismo , Proteínas Arqueales/antagonistas & inhibidores , Proteínas Arqueales/química , Proteínas Arqueales/genética , Proteínas Arqueales/metabolismo , Proteínas Bacterianas/antagonistas & inhibidores , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Sitios de Unión , Calorimetría , Relación Dosis-Respuesta a Droga , Escherichia coli , Bacilos Gramnegativos Anaerobios Rectos, Curvos y Espirales/química , Interacciones Hidrofóbicas e Hidrofílicas , Modelos Moleculares , Unión Proteica , Pyrococcus furiosus/química , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Tensoactivos/farmacología , beta-Glucosidasa/antagonistas & inhibidores , beta-Glucosidasa/química , beta-Glucosidasa/genética

RESUMEN

The ß-glucosidases are important enzymes employed in a large number of processes and industrial applications, including biofuel production from biomass. Therefore, in this study, we reported for the first time the photobiosynthesis of stable and functional silver/silver chloride nanoparticles (Ag/AgCl-NPs) using two hyperthermostable bacterial ß-glucosidases with industrial potential. The syntheses were straightforward and rapid processes carried out by mixing ß-glucosidase and silver nitrate (in buffer 10mM Tris-HCl, pH 8) under irradiation with light (over a wavelength range of 450-600nm), therefore, compatible with the green chemistry procedure. Synthesized Ag/AgCl-NPs were characterized using a series of physical techniques. Absorption spectroscopy showed a strong absorption band centered at 460nm due to surface plasmon resonance of the Ag-NPs. X-ray diffraction analysis revealed that the Ag/AgCl-NPs were purely crystalline in nature. Under electron microscopy, Ag/AgCl-NPs of variable diameter ranging from 10 to 100nm can be visualized. Furthermore, electron microscopy, zeta potential and Fourier transform infrared spectroscopy results confirmed the presence of ß-glucosidases coating and stabilizing the Ag/AgCl-NPs. Finally, the results showed that the enzymatic activities were maintained in the ß-glucosidases assisted Ag/AgCl-NPs. The information described here should provide a useful basis for future studies of ß-glucosidases assisted Ag/AgCl-NPs, including biotechnological applications.

Asunto(s)

Luz , Nanopartículas del Metal/química , Compuestos de Plata/química , Compuestos de Plata/metabolismo , Plata/química , Temperatura , beta-Glucosidasa/metabolismo , Bacilos Gramnegativos Anaerobios Rectos, Curvos y Espirales/metabolismo , Bacilos Gramnegativos Anaerobios Rectos, Curvos y Espirales/efectos de la radiación , Industrias , Modelos Moleculares , Conformación Proteica , beta-Glucosidasa/química

RESUMEN

Termites are considered one of the most efficient decomposers of lignocelluloses on Earth due to their ability to produce, along with its microbial symbionts, a repertoire of carbohydrate-active enzymes (CAZymes). Recently, a set of Pro-oxidant, Antioxidant, and Detoxification enzymes (PAD) were also correlated with the metabolism of carbohydrates and lignin in termites. The lower termite Coptotermes gestroi is considered the main urban pest in Brazil, causing damage to wood constructions. Recently, analysis of the enzymatic repertoire of C. gestroi unveiled the presence of different CAZymes. Because the gene profile of CAZy/PAD enzymes endogenously synthesized by C. gestroi and also by their symbiotic protists remains unclear, the aim of this study was to explore the eukaryotic repertoire of these enzymes in worker and soldier castes of C. gestroi. Our findings showed that worker and soldier castes present similar repertoires of CAZy/PAD enzymes, and also confirmed that endo-glucanases (GH9) and beta-glucosidases (GH1) were the most important glycoside hydrolase families related to lignocellulose degradation in both castes. Classical cellulases such as exo-glucanases (GH7) and endo-glucanases (GH5 and GH45), as well as classical xylanases (GH10 and GH11), were found in both castes only taxonomically related to protists, highlighting the importance of symbiosis in C. gestroi. Moreover, our analysis revealed the presence of Auxiliary Activity enzyme families (AAs), which could be related to lignin modifications in termite digestomes. In conclusion, this report expanded the knowledge on genes and proteins related to CAZy/PAD enzymes from worker and soldier castes of lower termites, revealing new potential enzyme candidates for second-generation biofuel processes.

RESUMEN

Fungal GH12 enzymes are classified as xyloglucanases when they specifically target xyloglucans, or promiscuous endoglucanases when they exhibit catalytic activity against xyloglucan and ß-glucan chains. Several structural and functional studies involving GH12 enzymes tried to explain the main patterns of xyloglucan activity, but what really determines xyloglucanase specificity remains elusive. Here, three fungal GH12 enzymes from Aspergillus clavatus (AclaXegA), A. zonatus (AspzoGH12), and A. terreus (AtEglD) were studied to unveil the molecular basis for substrate specificity. Using functional assays, site-directed mutagenesis, and molecular dynamics simulations, we demonstrated that three main regions are responsible for substrate selectivity: (i) the YSG group in loop 1; (ii) the SST group in loop 2; and (iii) loop A3-B3 and neighboring residues. Functional assays and sequence alignment showed that while AclaXegA is specific to xyloglucan, AtEglD cleaves ß-glucan, and xyloglucan. However, AspzoGH12 was also shown to be promiscuous contrarily to a sequence alignment-based prediction. We find that residues Y111 and R93 in AtEglD harbor the substrate in an adequate orientation for hydrolysis in the catalytic cleft entrance and that residues Y19 in AclaXegA and Y30 in AspzoGH12 partially compensate the absence of the YSG segment, typically found in promiscuous enzymes. The results point out the multiple structural factors underlying the substrate specificity of GH12 enzymes. Biotechnol. Bioeng. 2016;113: 2577-2586. © 2016 Wiley Periodicals, Inc.

Asunto(s)

Proteínas Fúngicas/química , Glucanos/química , Glucanos/ultraestructura , Glicósido Hidrolasas/química , Glicósido Hidrolasas/ultraestructura , Simulación del Acoplamiento Molecular , Xilanos/química , Xilanos/ultraestructura , Sitios de Unión , Activación Enzimática , Proteínas Fúngicas/metabolismo , Proteínas Fúngicas/ultraestructura , Glucanos/metabolismo , Glicósido Hidrolasas/metabolismo , Modelos Químicos , Unión Proteica , Conformación Proteica , Relación Estructura-Actividad , Especificidad por Sustrato , Xilanos/metabolismo

RESUMEN

Non-productive adsorption of cellulases onto lignins is an important mechanism that negatively affects the enzymatic hydrolysis of lignocellulose biomass. Here, we examined the non-productive adsorption of two bacterial ß-glucosidases (GH1 and GH3) on lignins. The results showed that ß-glucosidases can adsorb to lignins through different mechanisms. GH1 ß-glucosidase adsorption onto lignins was found to be strongly pH-dependent, suggesting that the adsorption is electrostatically modulated. For GH3 ß-glucosidase, the results suggested that the fibronectin type III-like domain interacts with lignins through electrostatic and hydrophobic interactions that can partially, or completely, overcome repulsive electrostatic forces between the catalytic domain and lignins. Finally, the increase of temperature did not result in the increase of ß-glucosidases adsorption, probably because there is no significant increase in hydrophobic regions in the ß-glucosidases structures. The data provided here can be useful for biotechnological applications, especially in the field of plant structural polysaccharides conversion into bioenergy and bioproducts.

Asunto(s)

Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Celulasas/química , Celulasas/metabolismo , Lignina/química , Lignina/metabolismo , Adsorción , Biocombustibles , Biomasa , Biotecnología , Dominio de Fibronectina del Tipo III , Concentración de Iones de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Modelos Moleculares , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Electricidad Estática , Temperatura

RESUMEN

CelE1 is a cold-active endo-acting glucanase with high activity at a broad temperature range and under alkaline conditions. Here, we examined the effects of pH on the secondary and tertiary structures, net charge, and activity of CelE1. Although variation in pH showed a small effect in the enzyme structure, the activity was highly influenced at acidic conditions, while reached the optimum activity at pH 8. Furthermore, to estimate whether CelE1 could be used as detergent additives, CelE1 activity was evaluated in the presence of surfactants. Ionic and nonionic surfactants were not able to reduce CelE1 activity significantly. Therefore, CelE1 was found to be promising candidate for use as detergent additives. Finally, we reported a thermodynamic analysis based on the structural stability and the chemical unfolding/refolding process of CelE1. The results indicated that the chemical unfolding proceeds as a reversible two-state process. These data can be useful for biotechnological applications.