Purification and characterization of an N-acetylglucosaminidase produced by a Trichoderma harzianum strain which controls Crinipellis perniciosa

Purification, identification and characterization of Nag2 N-acetylglucosaminidase from Trichoderma virens strain mango

BACKGROUND

N-acetylglucosaminidase (NAGase) could liberate N-acetylglucosamine (GlcNAc) from GlcNAc-containing oligosaccharides. Trichoderma spp. is an important source of chitinase, particularly NAGase for industrial use. nag1 and nag2 genes encoding NAGase, are found in the genome in Trichoderma spp. The deduced Nag1 and Nag2 shares ~ 55% homology in Trichoderma virens. Most studies were focus on Nag1 and nag1 previously.

RESULTS

The native NAGase (TvmNAG2) was purified to homogeneity with molecular mass of ~ 68 kDa on SDS-PAGE analysis, and identified as Nag2 by MALDI/MS analysis from an isolate T. virens strain mango. RT-PCR analyses revealed that only nag2 gene was expressed in liquid culture of T. virens, while both of nag1 and nag2 were expressed in T. virens cultured on the plates. TvmNAG2 was thermally stable up to 60 °C for 2 h, and the optimal pH and temperature were 5.0 and 60-65 °C, respectively, using p-nitrophenyl-N-acetyl-β-D-glucosaminide (pNP-NAG) as substrate. The hydrolytic product of colloidal chitin by TvmNAG2 was suggested to be GlcNAc based on TLC analyses. Moreover, TvmNAG2 possesses antifungal activity, inhibiting the mycelium growth of Sclerotium rolfsii. And it was resistant to the proteolysis by papain and trypsin.

CONCLUSIONS

The native Nag2, TvmNAG2 was purified and identified from T. virens strain mango, as well as enzymatic properties. To our knowledge, it is the first report with the properties of native Trichoderma Nag2.

Purification and characterization of chitinase produced by thermophilic fungi Thermomyces lanuginosus

BACKGROUND

In the past few years, the production of shrimp shell waste from the seafood processing industries has confronted a significant surge. Furthermore, insignificant dumping of waste has dangerous effects on both nature and human well-being. This marine waste contains a huge quantity of chitin which has several applications in different fields. The chitinase enzyme can achieve degradation of chitin, and the chitin itself can be used as the substrate as well for production of chitinase. In the current study, the chitinase enzyme was produced by Thermomyces lanuginosus. The extracellular chitinase was purified from crude extract using ammonium sulfate precipitation followed by DEAE-cellulose ion-exchange chromatography and Sephadex G-100 gel filtration chromatography. The stability and activity of chitinase with different pH, temperature, different times for a reaction, in the presence of different metal ions, and different concentration of enzyme and substrate were analyzed.

RESULT

The chitinase activity was found to be highest at pH 6.5, 50 °C, and 60 min after the reaction began. and the chitinase showed the highest activity and stability in the presence of β-mercaptoethanol (ME). The SDS-PAGE of denatured purified chitinase showed a protein band of 18 kDa.

CONCLUSION

The characterization study concludes that Cu²⁺, Hg²⁺, and EDTA have an inhibitory effect on chitinase activity, whereas β-ME acts as an activator for chitinase activity. The utilization of chitin to produce chitinase and the degradation of chitin using that chitinase enzyme would be an opportunity for bioremediation of shrimp shell waste.

Heterologous expression and characterization of thermostable chitinase and β-N-acetylhexosaminidase from Caldicellulosiruptor acetigenus and their synergistic action on the bioconversion of chitin into N-acetyl-d-glucosamine

The bioconversion of chitin into N-acetyl-d-glucosamine (GlcNAc) using chitinolytic enzymes is one of the important avenues for chitin valorization. However, industrial applications of chitinolytic enzymes have been limited by their poor thermostability. Therefore, it is necessary to discover thermostable chitinolytic enzymes for GlcNAc production from chitin. In this study, two chitinolytic enzyme-encoding genes CaChiT and CaHex from Caldicellulosiruptor acetigenus were identified and heterologously expressed in Escherichia coli. The purified recombinant CaChiT and CaHex showed optimal activities at 70 °C and 90 °C respectively, and exhibited good thermostability over a range of temperature below 70 °C and broad pH stability at pH range of 3.0-8.0. CaChiT and CaHex were active on colloidal chitin, pNP-(GlcNAc)₂, pNP-(GlcNAc)₃, and pNP-GlcNAc, pNP-(GlcNAc)₂, pNP-(GlcNAc)₃, pNP-Glc respectively. Besides, the chitin oligosaccharides and colloidal chitin hydrolysis profiles revealed that CaChiT degraded chitin chains through exo-mode of action. Furthermore, CaChiT and CaHex exhibited a synergistic effect in the degradation of colloidal chitin, reaching 0.60 mg/mL of GlcNAc production after 1 h incubation. These results suggested that a combination of CaChiT and CaHex have great potential for industrial applications in the enzymatic production of GlcNAc from chitin-containing biowastes.

Use of Trichoderma koningiopsis chitinase to enhance the insecticidal activity of Beauveria bassiana against Diatraea saccharalis

Trichoderma is a well-known soil-borne fungus, highly efficient producer of extracellular enzymes including chitinases. The aim of this study was to recover a chitinase from fermentation waste after harvesting Trichoderma koningiopsis Th003 conidia and assess its potential as an enhancer of Beauveria bassiana insecticidal activity against Diatraea saccharalis. T. koningiopsis was produced by solid fermentation, conidia were harvested, and a crude extract (CE) was recovered by washing the residual substrate (rice:wheat bran). The partially purified chitinase (PPC) (75 kDa product) with N-acetyl-β-glucosaminidase activity was obtained by chromatography to 29.3-fold with optimal activity at pH 5 and 55°C. Both the CE and the PPC were mixed with B. bassiana Bv062 conidia and assessed in a bioassay against D. saccharalis larvae. The CE and PPC from T. koningiopsis Th003 did not affect the germination or viability of B. bassiana conidia and enhanced its insecticidal activity when used at 0.06 U/ml enzymatic activity with a 24.5% reduction in B. bassiana lethal time (LT₉₀ ). This study demonstrated the potential of chitinases produced by T. koningiopsis in solid fermentation to be recovered from the waste substrate and used as an additive to enhance B. bassiana, adding value to the main waste from the Trichoderma biopesticide/biofertilizer industries.

Purification and biochemical/biophysical characterization of two hexosaminidases from the fresh water mussel, Lamellidens corrianus

Two thermostable isoforms of a hexosaminidase were purified to homogeneity from the soluble extract of fresh water mussel Lamellidens corrianus, employing a variety of chromatographic techniques. Hexosaminidase A (HexA) is a heterodimer with subunit masses of ~80 and 55 kDa. Hexosaminidase B (HexB) is a homodimer with a subunit mass of 55-60 kDa. Circular dichroism spectroscopic studies indicated that both HexA and HexB contain β-sheet as the major secondary structural component with considerably lower content of α-helix. The temperature and pH optima of both the isoforms were found to be 60 °C and 4.0, respectively. The IC₅₀ values for HexA with N-acetyl-d-galactosamine, N-acetyl-d-glucosamine, d-galactosamine, d-glucosamine, methyl α-d-mannopyranoside and d-mannose are 3.7, 72.8, 307, 216, 244 and 128 mM, respectively, whereas the corresponding IC₅₀ values for HexB were estimated as 5.1, 61, 68, 190, 92 and 133 mM, respectively. Kinetic parameters K_M and V_max for HexA and B with p-nitrophenyl N-acetyl-β-d-glucosaminide are 4 mM, 0.23 μmol·min^-1·mL^-1 and 2.86 mM, 0.29 μmol·min^-1·mL^-1, respectively, and with p-nitrophenyl N-acetyl-β-d-galactosaminide are 4.5 mM, 0.054 μmol·min^-1·mL^-1 and 1.4 mM, 0.14 μmol·min^-1·mL^-1, respectively. GalNAc inhibited both isoforms in a non-competitive manner, whereas a mixed mode of inhibition was observed with GlcNAc with both forms.

Identification and Characterization of a β-N-Acetylhexosaminidase with a Biosynthetic Activity from the Marine Bacterium Paraglaciecola hydrolytica S66T

β-N-Acetylhexosaminidases are glycoside hydrolases (GHs) acting on N-acetylated carbohydrates and glycoproteins with the release of N-acetylhexosamines. Members of the family GH20 have been reported to catalyze the transfer of N-acetylglucosamine (GlcNAc) to an acceptor, i.e., the reverse of hydrolysis, thus representing an alternative to chemical oligosaccharide synthesis. Two putative GH20 β-N-acetylhexosaminidases, PhNah20A and PhNah20B, encoded by the marine bacterium Paraglaciecola hydrolytica S66^T, are distantly related to previously characterized enzymes. Remarkably, PhNah20A was located by phylogenetic analysis outside clusters of other studied β-N-acetylhexosaminidases, in a unique position between bacterial and eukaryotic enzymes. We successfully produced recombinant PhNah20A showing optimum activity at pH 6.0 and 50 °C, hydrolysis of GlcNAc β-1,4 and β-1,3 linkages in chitobiose (GlcNAc)₂ and GlcNAc-1,3-β-Gal-1,4-β-Glc (LNT2), a human milk oligosaccharide core structure. The kinetic parameters of PhNah20A for p-nitrophenyl-GlcNAc and p-nitrophenyl-GalNAc were highly similar: k_cat/K_M being 341 and 344 mM⁻¹·s⁻¹, respectively. PhNah20A was unstable in dilute solution, but retained full activity in the presence of 0.5% bovine serum albumin (BSA). PhNah20A catalyzed the formation of LNT2, the non-reducing trisaccharide β-Gal-1,4-β-Glc-1,1-β-GlcNAc, and in low amounts the β-1,2- or β-1,3-linked trisaccharide β-Gal-1,4(β-GlcNAc)-1,x-Glc by a transglycosylation of lactose using 2-methyl-(1,2-dideoxy-α-d-glucopyrano)-oxazoline (NAG-oxazoline) as the donor. PhNah20A is the first characterized member of a distinct subgroup within GH20 β-N-acetylhexosaminidases.

Characterization of Stackebrandtia nassauensis GH 20 Beta-Hexosaminidase, a Versatile Biocatalyst for Chitobiose Degradation

An unstudied β-N-acetylhexosaminidase (SnHex) from the soil bacterium Stackebrandtia nassauensis was successfully cloned and subsequently expressed as a soluble protein in Escherichia coli. Activity tests and the biochemical characterization of the purified protein revealed an optimum pH of 6.0 and a robust thermal stability at 50 °C within 24 h. The addition of urea (1 M) or sodium dodecyl sulfate (1% w/v) reduced the activity of the enzyme by 44% and 58%, respectively, whereas the addition of divalent metal ions had no effect on the enzymatic activity. PUGNAc (O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate) strongly inhibited the enzyme in sub-micromolar concentrations. The β-N-acetylhexosaminidase was able to hydrolyze β1,2-linked, β1,3-linked, β1,4-linked, and β1,6-linked GlcNAc residues from the non-reducing end of various tested glycan standards, including bisecting GlcNAc from one of the tested hybrid-type N-glycan substrates. A mutational study revealed that the amino acids D306 and E307 bear the catalytically relevant side acid/base side chains. When coupled with a chitinase, the β-N-acetylhexosaminidase was able to generate GlcNAc directly from colloidal chitin, which showed the potential of this enzyme for biotechnological applications.

β-N-Acetylglucosaminidase MthNAG from Myceliophthora thermophila C1, a thermostable enzyme for production of N-acetylglucosamine from chitin

Thermostable enzymes are a promising alternative for chemical catalysts currently used for the production of N-acetylglucosamine (GlcNAc) from chitin. In this study, a novel thermostable β-N-acetylglucosaminidase MthNAG was cloned and purified from the thermophilic fungus Myceliophthora thermophila C1. MthNAG is a protein with a molecular weight of 71 kDa as determined with MALDI-TOF-MS. MthNAG has the highest activity at 50 °C and pH 4.5. The enzyme shows high thermostability above the optimum temperature: at 55 °C (144 h, 75% activity), 60 °C (48 h, 85% activity; half-life 82 h), and 70 °C (24 h, 33% activity; half-life 18 h). MthNAG releases GlcNAc from chitin oligosaccharides (GlcNAc)_2–5, p-nitrophenol derivatives of chitin oligosaccharides (GlcNAc)_1–3-pNP, and the polymeric substrates swollen chitin and soluble chitosan. The highest activity was detected towards (GlcNAc)₂. MthNAG released GlcNAc from the non-reducing end of the substrate. We found that MthNAG and Chitinase Chi1 from M. thermophila C1 synergistically degraded swollen chitin and released GlcNAc in concentration of approximately 130 times higher than when only MthNAG was used. Therefore, chitinase Chi1 and MthNAG have great potential in the industrial production of GlcNAc.

Enzymatic properties of β-N-acetylglucosaminidases

β-N-Acetylglucosaminidases (GlcNAcases) hydrolyse N-acetylglucosamine-containing oligosaccharides and proteins. These enzymes produce N-acetylglucosamine (GlcNAc) and have a wide range of promising applications in the food, energy, and pharmaceutical industries, such as synergistic degradation of chitin with endo-chitinases and using GlcNAc to produce sialic acid, bioethanol, single-cell proteins, and pharmaceutical therapeutics. GlcNAcases also play an important role in the dynamic balance of cellular O-linked GlcNAc levels, catabolism of ganglioside storage in Tay-Sachs disease, and bacterial cell wall recycling and flagellar assembly. In view of these important biological functions and the wide range of industrial applications of GlcNAcases, this review aims to provide a better understanding of various advances for these enzymes. It focuses on enzymatic properties of GlcNAcases, including substrate specificity, catalytic activity, pH optimum, temperature optimum, thermostability, the effects of various metal ions and organic reagents, and transglycosylation.

Toxoplasma gondii Chitinase Induces Macrophage Activation

Toxoplasma gondii is an obligate intracellular protozoan parasite found worldwide that is able to chronically infect almost all vertebrate species, especially birds and mammalians. Chitinases are essential to various biological processes, and some pathogens rely on chitinases for successful parasitization. Here, we purified and characterized a chitinase from T. gondii. The enzyme, provisionally named Tg_chitinase, has a molecular mass of 13.7 kDa and exhibits a Km of 0.34 mM and a Vmax of 2.64. The optimal environmental conditions for enzymatic function were at pH 4.0 and 50 °C. Tg_chitinase was immunolocalized in the cytoplasm of highly virulent T. gondii RH strain tachyzoites, mainly at the apical extremity. Tg_chitinase induced macrophage activation as manifested by the production of high levels of pro-inflammatory cytokines, a pathogenic hallmark of T. gondii infection. In conclusion, to our knowledge, we describe for the first time a chitinase of T. gondii tachyzoites and provide evidence that this enzyme might influence the pathogenesis of T. gondii infection.

Characterization and homologous overexpression of an N-acetylglucosaminidase Nag1 from Trichoderma reesei

Trichoderma reesei is thought to be a promising recombinant host for the production and secretion of complex proteins due to its ability to secrete large amounts of proteins. In this study we identified a functional N-acetyl-β-glucosaminidase (NAGase) gene Nag1 in T. reesei. Nag1, a putative gene encoding a GH 20 family NAGase in T. reesei, was cloned and homologous overexpressed in the T. reesei RutC30ΔU3 with a strong cellobiohydrolase1 gene (cbh1) promoter. Nag1 was secreted in its active form and the highest expression level was around 499.85IU/ml. Nag1 has a molecular mass of 80kDa. The optimum pH and temperature were 4.0 and 60°C, respectively.

Chitinases: in agriculture and human healthcare

Biological control of phytopathogenic fungi and insects continues to inspire the research and development of environmentally friendly bioactive alternatives. Potentially lytic enzymes, chitinases can act as a biocontrol agent against agriculturally important fungi and insects. The cell wall in fungi and protective covers, i.e. cuticle in insects shares a key structural polymer, chitin, a β-1,4-linked N-acetylglucosamine polymer. Therefore, it is advantageous to develop a common biocontrol agent against both of these groups. As chitin is absent in plants and mammals, targeting its metabolism will signify an eco-friendly strategy for the control of agriculturally important fungi and insects but is innocuous to mammals, plants, beneficial insects and other organisms. In addition, development of chitinase transgenic plant varieties probably holds the most promising method for augmenting agricultural crop protection and productivity, when properly integrated into traditional systems. Recently, human proteins with chitinase activity and chitinase-like proteins were identified and established as biomarkers for human diseases. This review covers the recent advances of chitinases as a biocontrol agent and its various applications including preparation of medically important chitooligosaccharides, bioconversion of chitin as well as in implementing chitinases as diagnostic and prognostic markers for numerous diseases and the prospect of their future utilization.

RNA interference of endochitinases in the sugarcane endophyte Trichoderma virens 223 reduces its fitness as a biocontrol agent of pineapple disease

The sugarcane root endophyte Trichoderma virens 223 holds enormous potential as a sustainable alternative to chemical pesticides in the control of sugarcane diseases. Its efficacy as a biocontrol agent is thought to be associated with its production of chitinase enzymes, including N-acetyl-ß-D-glucosaminidases, chitobiosidases and endochitinases. We used targeted gene deletion and RNA-dependent gene silencing strategies to disrupt N-acetyl-ß-D-glucosaminidase and endochitinase activities of the fungus, and to determine their roles in the biocontrol of soil-borne plant pathogens. The loss of N-acetyl-ß-D-glucosaminidase activities was dispensable for biocontrol of the plurivorous damping-off pathogens Rhizoctonia solani and Sclerotinia sclerotiorum, and of the sugarcane pathogen Ceratocystis paradoxa, the causal agent of pineapple disease. Similarly, suppression of endochitinase activities had no effect on R. solani and S. sclerotiorum disease control, but had a pronounced effect on the ability of T. virens 223 to control pineapple disease. Our work demonstrates a critical requirement for T. virens 223 endochitinase activity in the biocontrol of C. paradoxa sugarcane disease, but not for general antagonism of other soil pathogens. This may reflect its lifestyle as a sugarcane root endophyte.

The design of oligonucleotide primers for the universal amplification of the N-acetylglucosaminidase gene (nag1) in Chytridiomycetes with emphasis on the anaerobic Neocallimastigales

The common feature of all chytridiomycetous fungi, aerobic as well as anaerobic, is an abundance of chitin in their cell wall. The genes coding for chitinases have therefore been widely used as phylogenetic markers in ascomycetes. As their utility for Chytridiomycetes has not been determined we chose the gene encoding an enzyme involved in chitin degradation and energy metabolism, the beta-(1,4)-N-acetylglucosaminidase (nag1). Primer pair Nag-forward and Nag-reverse was used to create PCR product from 5 strains of anaerobic and 7 strains of aerobic chytrids. However, Blast search of sequenced amplicons showed that these primers are specific only for fungus Emericella nidulans. Amino acid alignment of Nag1 proteins of fungal, protozoal and bacterial origin available in GenBank database was therefore performed. Five amino acid regions were found to be conserved enough to serve as a suitable domain for the design of a set of primers for the universal amplification of the nag1 gene in the Neocallimastigales fungi.

Phylogenetic analyses suggest multiple changes of substrate specificity within the glycosyl hydrolase 20 family

Background

Beta-N-acetylhexosaminidases belonging to the glycosyl hydrolase 20 (GH20) family are involved in the removal of terminal β-glycosidacally linked N-acetylhexosamine residues. These enzymes, widely distributed in microorganisms, animals and plants, are involved in many important physiological and pathological processes, such as cell structural integrity, energy storage, pathogen defence, viral penetration, cellular signalling, fertilization, development of carcinomas, inflammatory events and lysosomal storage diseases. Nevertheless, only limited analyses of phylogenetic relationships between GH20 genes have been performed until now.

Results

Careful phylogenetic analyses of 233 inferred protein sequences from eukaryotes and prokaryotes reveal a complex history for the GH20 family. In bacteria, multiple gene duplications and lineage specific gene loss (and/or horizontal gene transfer) are required to explain the observed taxonomic distribution. The last common ancestor of extant eukaryotes is likely to have possessed at least one GH20 family member. At least one gene duplication before the divergence of animals, plants and fungi as well as other lineage specific duplication events have given rise to multiple paralogous subfamilies in eukaryotes. Phylogenetic analyses also suggest that a second, divergent subfamily of GH20 family genes present in animals derive from an independent prokaryotic source. Our data suggest multiple convergent changes of functional roles of GH20 family members in eukaryotes.

Conclusion

This study represents the first detailed evolutionary analysis of the glycosyl hydrolase GH20 family. Mapping of data concerning physiological function of GH20 family members onto the phylogenetic tree reveals that apparently convergent and highly lineage specific changes in substrate specificity have occurred in multiple GH20 subfamilies.

Review of fungal chitinases

Chitin is the second most abundant organic and renewable source in nature, after cellulose. Chitinases are chitin-degrading enzymes. Chitinases have important biophysiological functions and immense potential applications. In recent years, researches on fungal chitinases have made fast progress, especially in molecular levels. Therefore, the present review will focus on recent advances of fungal chitinases, containing their nomenclature and assays, purification and characterization, molecular cloning and expression, family and structure, regulation, and function and application.