Mechanism of action of theendo-(1 → 3)-α-glucanase MutAp from the mycoparasitic fungusTrichoderma harzianum

Evolution and phylogenetic distribution of endo-α-mannosidase

While glycans underlie many biological processes, such as protein folding, cell adhesion, and cell-cell recognition, deep evolution of glycosylation machinery remains an understudied topic. N-linked glycosylation is a conserved process in which mannosidases are key trimming enzymes. One of them is the glycoprotein endo-α-1,2-mannosidase which participates in the initial trimming of mannose moieties from an N-linked glycan inside the cis-Golgi. It is unique as the only endo-acting mannosidase found in this organelle. Relatively little is known about its origins and evolutionary history; so far it was reported to occur only in vertebrates. In this work, a taxon-rich bioinformatic survey to unravel the evolutionary history of this enzyme, including all major eukaryotic clades and a wide representation of animals, is presented. The endomannosidase was found to be more widely distributed in animals and other eukaryotes. The protein motif changes in context of the canonical animal enzyme were tracked. Additionally, the data show the two canonical vertebrate endomannosidase genes, MANEA and MANEAL, arose at the second round of the two vertebrate genome duplications and one more vertebrate paralog, CMANEAL, is uncovered. Finally, a framework where N-glycosylation co-evolved with complex multicellularity is described. A better understanding of the evolution of core glycosylation pathways is pivotal to understanding biology of eukaryotes in general, and the Golgi apparatus in particular. This systematic analysis of the endomannosidase evolution is one step toward this goal.

Heterologous expression of α-1,3-glucanase Agn1p from Schizosaccharomyces pombe, and efficient production of nigero-oligosaccharides by enzymatic hydrolysis from solubilized α-1,3;1,6-glucan

The glycoside hydrolase family 71 α-1,3-glucanase (Agn1p) of Schizosaccharomyces pombe was expressed in Escherichia coli Rosetta-gami B (DE3). Agn1p (0.5 nmol/mL) hydrolyzed insoluble α-1,3-glucan (1%), and about 3.3 mm reducing sugars were released after 1440 min of reaction. The analysis of reaction products by high-performance liquid chromatography revealed that pentasaccharides accumulated in the reaction mixture as the main products, along with a small amount of mono-, di-, tri-, tetra-, and hexasaccharides. Soluble glucan was prepared from insoluble α-1,3;1,6-glucan by alkaline and sonication treatment to improve the hydrolytic efficiency. As a result, this solubilized α-1,3;1,6-glucan maintained a solubilized state for at least 6 h. Agn1p (0.5 nmol/mL) hydrolyzed the solubilized α-1,3;1,6-glucan (1%), and about 8.2 mm reducing sugars were released after 240 min of reaction. Moreover, Agn1p released about 12.3 mm reducing sugars from 2% of the solubilized α-1,3;1,6-glucan.

Mutanase from Trichoderma harzianum inductively Produced by Mutan: Short-Term Treatment to Degrade Mature Streptococcus mutans Biofilm

This study aimed to evaluate the disruptive effect of fungal mutanase against cariogenic biofilm after short-term treatment. For that, mature Streptococcus mutans biofilms (n = 9) were exposed to active or inactivated enzymes produced by Trichoderma harzianum for 1 min, two times per day. Biofilms were analyzed by amount of matrix water-insoluble polysaccharides, bacterial viability, acidogenicity, and morphology by scanning electron microscopy (SEM). The group treated with active enzymes (AE) had a significantly lower amount of insoluble polysaccharides (893.30 ± 293.69) when compared to the negative control group (NaCl, 2192.59 ± 361.96), yet no significant difference was found when comparing to the positive control group (CHX, 436.82 ± 151.07). Also, there was no significant effect on bacteria metabolism and viability (P-value < 0.05). Data generated by the quantitative analysis were confirmed through scanning electron microscopy images. Thus, fungal mutanase degraded the biofilm after a short-term treatment without interfering with bacterial viability and metabolism. Such findings offer insight to the development of routine oral care products containing this input.

Molecular interaction between plants and Trichoderma species against soil-borne plant pathogens

Trichoderma spp. (Hypocreales) are used worldwide as a lucrative biocontrol agent. The interactions of Trichoderma spp. with host plants and pathogens at a molecular level are important in understanding the various mechanisms adopted by the fungus to attain a close relationship with their plant host through superior antifungal/antimicrobial activity. When working in synchrony, mycoparasitism, antibiosis, competition, and the induction of a systemic acquired resistance (SAR)-like response are considered key factors in deciding the biocontrol potential of Trichoderma. Sucrose-rich root exudates of the host plant attract Trichoderma. The soluble secretome of Trichoderma plays a significant role in attachment to and penetration and colonization of plant roots, as well as modulating the mycoparasitic and antibiosis activity of Trichoderma. This review aims to gather information on how Trichoderma interacts with host plants and its role as a biocontrol agent of soil-borne phytopathogens, and to give a comprehensive account of the diverse molecular aspects of this interaction.

Glycoside hydrolases active on microbial exopolysaccharide α-glucans: structures and function

Glucose is the most abundant monosaccharide in nature and is an important energy source for living organisms. Glucose exists primarily as oligomers or polymers and organisms break it down and consume it. Starch is an important plant-derived α-glucan in the human diet. The enzymes that degrade this α-glucan have been well studied as they are ubiquitous throughout nature. Some bacteria and fungi produce α-glucans with different glucosidic linkages compared with that of starch, and their structures are quite complex and not fully understood. Compared with enzymes that degrade the α-(1→4) and α-(1→6) linkages in starch, biochemical and structural studies of the enzymes that catabolize α-glucans from these microorganisms are limited. This review focuses on glycoside hydrolases that act on microbial exopolysaccharide α-glucans containing α-(1→6), α-(1→3), and α-(1→2) linkages. Recently acquired information regarding microbial genomes has contributed to the discovery of enzymes with new substrate specificities compared with that of previously studied enzymes. The discovery of new microbial α-glucan-hydrolyzing enzymes suggests previously unknown carbohydrate utilization pathways and reveals strategies for microorganisms to obtain energy from external sources. In addition, structural analysis of α-glucan degrading enzymes has revealed their substrate recognition mechanisms and expanded their potential use as tools for understanding complex carbohydrate structures. In this review, the author summarizes the recent progress in the structural biology of microbial α-glucan degrading enzymes, touching on previous studies of microbial α-glucan degrading enzymes.

Crystal structure of the catalytic unit of GH 87-type α-1,3-glucanase Agl-KA from Bacillus circulans

Glycoside hydrolase (GH) 87-type α-1,3-glucanase hydrolyses the α-1,3-glucoside linkages of α-1,3-glucan, which is found in fungal cell walls and extracellular polysaccharides produced by oral Streptococci. In this study, we report on the molecular structure of the catalytic unit of GH 87-type α-1,3-glucanase, Agl-KA, from Bacillus circulans, as determined by x-ray crystallography at a resolution of 1.82 Å. The catalytic unit constitutes a complex structure of two tandemly connected domains-the N-terminal galactose-binding-like domain and the C-terminal right-handed β-helix domain. While the β-helix domain is widely found among polysaccharide-processing enzymes, complex formation with the galactose-binding-like domain was observed for the first time. Biochemical assays showed that Asp1067, Asp1090 and Asp1091 are important for catalysis, and these residues are indeed located at the putative substrate-binding cleft, which forms a closed end and explains the product specificity.

Deletion of uncharacterized domain from α-1,3-glucanase of Bacillus circulans KA-304 enhances heterologous enzyme production in Escherichia coli

α-1,3-Glucanase (Agl-KA) of Bacillus circulans KA-304 consists of an N-terminal discoidin domain (DS1), a carbohydrate binding module family 6 (CBM6), threonine and proline repeats (TP), a second discoidin domain (DS2), an uncharacterized conserved domain (UCD), and a C-terminal catalytic domain. Previously, we reported that DS1, CBM6, and DS2 have α-1,3-glucan-binding activity and contribute to α-1,3-glucan hydrolysis. In this study, UCD deletion mutant (AglΔUCD) was constructed, and its properties were compared with those of Agl-KA. α-1,3-Glucan hydrolyzing, α-1,3-glucan binding, and protoplast-forming activities of AglΔUCD were almost the same as those of Agl-KA. k_cat/K_m values of AgΔUCD and Agl-KA were 11.4 and 11.1 s^-1 mg^-1 mL, respectively. AglΔUCD and Agl-KA exhibited similar characteristics, such as optimal pH, pH stability, optimal temperature, and thermostability. These results suggest that UCD is not α-1,3-glucan-binding and flexible linker domain, and that deletion of UCD does not affect the affinity of N-terminal binding domains and the catalytic action of the C-terminal domain. Subsequently, heterologous UCenzyme productivity of AglΔD in Escherichia coli was compared with that of Agl-KA. The productivity of AglΔUCD was about 4-fold larger than that of Agl-KA after an 8-h induction at 30°C. In the case of induction at 20°C, the productivity of AglΔUCD was also larger than that of Agl-KA. These findings indicate that deletion of only UCD enhances the enzyme productivity in E. coli.

Integrated Translatome and Proteome: Approach for Accurate Portraying of Widespread Multifunctional Aspects of Trichoderma

Genome-wide studies of transcripts expression help in systematic monitoring of genes and allow targeting of candidate genes for future research. In contrast to relatively stable genomic data, the expression of genes is dynamic and regulated both at time and space level at different level in. The variation in the rate of translation is specific for each protein. Both the inherent nature of an mRNA molecule to be translated and the external environmental stimuli can affect the efficiency of the translation process. In biocontrol agents (BCAs), the molecular response at translational level may represents noise-like response of absolute transcript level and an adaptive response to physiological and pathological situations representing subset of mRNAs population actively translated in a cell. The molecular responses of biocontrol are complex and involve multistage regulation of number of genes. The use of high-throughput techniques has led to rapid increase in volume of transcriptomics data of Trichoderma. In general, almost half of the variations of transcriptome and protein level are due to translational control. Thus, studies are required to integrate raw information from different “omics” approaches for accurate depiction of translational response of BCAs in interaction with plants and plant pathogens. The studies on translational status of only active mRNAs bridging with proteome data will help in accurate characterization of only a subset of mRNAs actively engaged in translation. This review highlights the associated bottlenecks and use of state-of-the-art procedures in addressing the gap to accelerate future accomplishment of biocontrol mechanisms.

Enzymes in therapy of biofilm-related oral diseases

Biofilm-related infections of the oral cavity, including dental caries and periodontitis, represent the most prevalent health problems. For years, the treatment thereof was largely based on antibacterial chemical agents. Recently, however, there has been growing interest in the application of more preventive and minimally invasive biotechnological methods. This review focuses on the potential applications of enzymes in the treatment and prevention of oral diseases. Dental plaque is a microbial community that develops on the tooth surface, embedded in a matrix of extracellular polymeric substances of bacterial and host origin. Both cariogenic microorganisms and the key components of oral biofilm matrix may be the targets of the enzymes. Oxidative salivary enzymes inhibit or limit the growth of oral pathogens, thereby supporting the natural host defense system; polysaccharide hydrolases (mutanases and dextranases) degrade important carbohydrate components of the biofilm matrix, whereas proteases disrupt bacterial adhesion to oral surfaces or affect cell-cell interactions. The efficiency of the enzymes in in vitro and in vivo studies, advantages and limitations, as well as future perspectives for improving the enzymatic strategy are discussed.

α-1,3-Glucanase: present situation and prospect of research

α-1,3-Glucanases hydrolyze α-1,3-glucan which is an insoluble linear α-1,3-linked homopolymer of glucose and these enzymes are classified into two families of glycoside hydrolases on the basis of amino acid sequence similarity; type-71 α-1,3-glucanases found in fungi and type-87 enzymes in bacteria. α-1,3-Glucan (also called 'mutan') is a major component of dental plaque formed by oral Streptococci and has important physiological roles in various fungal species, including as a component of cell walls, an endogenous carbon source for sexual development, and a virulent factor. Considering these backgrounds, α-1,3-glucanases have been investigated from the perspectives of applications to dental care and development of cell-wall lytic enzymes. Compared with information regarding other glycoside hydrolases such as amylases, cellulases, chitinases, and β-glucanases, there is limited biochemical and structural information available regarding α-1,3-glucanase. Further research on α-1,3-glucanases on enzyme application to dental care and biological control of pathogenic fungi is expected. In this mini-review, we briefly describe how α-1,3-glucanases are categorized and characterized and present our study findings regarding α-1,3-glucanase from Bacillus circulans KA-304. Furthermore, we briefly discuss potential future applications of α-1,3-glucanases.

(1→3)-α-D-Glucan hydrolases in dental biofilm prevention and control: A review

Dental plaque is a highly diverse biofilm, which has an important function in maintenance of oral and systemic health but in some conditions becomes a cause of oral diseases. In addition to mechanical plaque removal, current methods of dental plaque control involve the use of chemical agents against biofilm pathogens, which however, given the complexity of the oral microbiome, is not sufficiently effective. Hence, there is a need for development of new anti-biofilm approaches. Polysaccharides, especially (1→3),(1→6)-α-D-glucans, which are key structural and functional constituents of the biofilm matrix, seem to be a good target for future therapeutic strategies. In this review, we have focused on (1→3)-α-glucanases, which can limit the cariogenic properties of the dental plaque extracellular polysaccharides. These enzymes are not widely known and have not been exhaustively described in literature.

Biochemical characterization of Paracoccidioides brasiliensis α-1,3-glucanase Agn1p, and its functionality by heterologous Expression in Schizosaccharomyces pombe

α-1,3-Glucan is present as the outermost layer of the cell wall in the pathogenic yeastlike (Y) form of Paracoccidioides brasiliensis. Based on experimental evidence, this polysaccharide has been proposed as a fungal virulence factor. To degrade α-1,3-glucan and allow remodeling of the cell wall, α-1,3-glucanase is required. Therefore, the study of this enzyme, its encoding gene, and regulatory mechanisms, might be of interest to understand the morphogenesis and virulence process in this fungus. A single gene, orthologous to other fungal α-1,3-glucanase genes, was identified in the Paracoccidioides genome, and labeled AGN1. Transcriptional levels of AGN1 and AGS1 (α-1,3-glucan synthase-encoding gene) increased sharply when the pathogenic Y phase was cultured in the presence of 5% horse serum, a reported booster for cell wall α-1,3-glucan synthesis in this fungus. To study the biochemical properties of P. brasiliensis Agn1p, the enzyme was heterologously overexpressed, purified, and its activity profile determined by means of the degradation of carboxymethyl α-1,3-glucan (SCMG, chemically modified from P. brasiliensis α-1,3-glucan), used as a soluble substrate for the enzymatic reaction. Inhibition assays, thin layer chromatography and enzymatic reactions with alternative substrates (dextran, starch, chitin, laminarin and cellulose), showed that Agn1p displays an endolytic cut pattern and high specificity for SCMG. Complementation of a Schizosaccharomyces pombe agn1Δ strain with the P. brasiliensis AGN1 gene restored the wild type phenotype, indicating functionality of the gene, suggesting a possible role of Agn1p in the remodeling of P. brasiliensis Y phase cell wall. Based on amino acid sequence, P. brasiliensis Agn1p, groups within the family 71 of fungal glycoside hydrolases (GH-71), showing similar biochemical characteristics to other members of this family. Also based on amino acid sequence alignments, we propose a subdivision of fungal GH-71 into at least five groups, for which specific conserved sequences can be identified.

Cloning, heterologous gene expression and biochemical characterization of the alpha-1,3-glucanase from the filamentous fungus Penicillium purpurogenum

There has been much recent interest in alpha-1,3-glucanases (mutanases) as they have the potential to be used in the treatment of dental caries. Mutanases have been reported in a number of bacteria, yeast and fungi but remain a relatively uncharacterised family of enzymes. In this study we heterologously expressed the mutanase gene from the filamentous fungus Penicillium purpurogenum to enable further characterization of its enzymatic activity. The mutanase cDNA was cloned and expressed in the methylotrophic yeast Pichia pastoris. The molecular mass of the secreted protein was about 102 kDa. The recombinant enzyme hydrolyzed mutan with a specific activity of 3.9 U/mg of protein. The recombinant enzyme was specific for mutan and could not cleave a variety of other polysaccharides demonstrating a specificity for alpha-1,3-glucosidic linkages. The pH and temperature optima were pH 4.6 and 45 degrees C, respectively. Synthetic compounds were also tested as substrates to assess whether the P. purpurogenum mutanase has an exo- or endo-type mechanism of hydrolysis. The results suggest an endo-hydrolytic mode of action. The type of mechanism was confirmed since mutanase activity was not suppressed in the presence of inhibitors of exo-type enzymes.

Role of the alpha-glucanase Agn2p in ascus-wall endolysis following sporulation in fission yeast

During sporulation in the ascomyceteous fungus Schizosaccharomyces pombe, diploid cells undergo differentiation into asci containing four haploid ascospores, which are highly resistant to environmental stresses. Although the morphogenetic processes involved in ascospore formation have been studied extensively, little is known about the molecular mechanism that ensures the release of mature ascospores from the ascus, allowing their dispersal into the environment. Recently, we identified Agn2p as the paralogue of the characterized endo-(1,3)-alpha-glucanase Agn1p, and observed that asci deleted for agn2 are defective in ascospore dispersal. Here, we focus on the cellular and biochemical functions of Agn2p. By placing agn2 under the control of an inducible promoter, we show that expression of agn2 is required for the efficient release of ascospores from their asci. Furthermore, we characterize the enzyme activity of purified recombinant Agn2p and show that Agn2p, like Agn1p, is an endo-(1,3)-alpha-glucanase that produces predominantly (1,3)-alpha-glucan pentasaccharides. Finally, we demonstrate that exogenous addition of purified Agn2p liberated the ascospores from asci deleted for agn2. We propose that Agn2p participates in the endolysis of the ascus wall by hydrolysing its (1,3)-alpha-glucan, thereby assisting in the release of ascospores.