Biochemical and genetic properties of Paenibacillus glycosyl hydrolase having chitosanase activity and discoidin domain

Role of Natural Binding Proteins in Therapy and Diagnostics

This review systematically investigates the critical role of natural binding proteins (NBPs), encompassing DNA-, RNA-, carbohydrate-, fatty acid-, and chitin-binding proteins, in the realms of oncology and diagnostics. In an era where cancer continues to pose significant challenges to healthcare systems worldwide, the innovative exploration of NBPs offers a promising frontier for advancing both the diagnostic accuracy and therapeutic efficacy of cancer management strategies. This manuscript provides an in-depth examination of the unique mechanisms by which NBPs interact with specific molecular targets, highlighting their potential to revolutionize cancer diagnostics and therapy. Furthermore, it discusses the burgeoning research on aptamers, demonstrating their utility as 'nucleic acid antibodies' for targeted therapy and precision diagnostics. Despite the promising applications of NBPs and aptamers in enhancing early cancer detection and developing personalized treatment protocols, this review identifies a critical knowledge gap: the need for comprehensive studies to understand the diverse functionalities and therapeutic potentials of NBPs across different cancer types and diagnostic scenarios. By bridging this gap, this manuscript underscores the importance of NBPs and aptamers in paving the way for next-generation diagnostics and targeted cancer treatments.

Chitosanase Production from the Liquid Fermentation of Squid Pens Waste by Paenibacillus elgii

Chitosanases play a significant part in the hydrolysis of chitosan to form chitooligosaccharides (COS) that possess diverse biological activities. This study aimed to enhance the productivity of Paenibacillus elgii TKU051 chitosanase by fermentation from chitinous fishery wastes. The ideal parameters for achieving maximum chitosanase activity were determined: a squid pens powder amount of 5.278% (w/v), an initial pH value of 8.93, an incubation temperature of 38 °C, and an incubation duration of 5.73 days. The resulting chitosanase activity of the culture medium was 2.023 U/mL. A chitosanase with a molecular weight of 25 kDa was isolated from the culture medium of P. elgii TKU051 and was biochemically characterized. Liquid chromatography with tandem mass spectrometry analysis revealed that P. elgii TKU051 chitosanase exhibited a maximum amino acid identity of 43% with a chitosanase of Bacillus circulans belonging to the glycoside hydrolase (GH) family 46. P. elgii TKU051 chitosanase demonstrated optimal activity at pH 5.5 while displaying remarkable stability within the pH range of 5.0 to 9.0. The enzyme displayed maximum efficiency at 60 °C and demonstrated considerable stability at temperatures ≤40 °C. The presence of Mn2+ positively affected the activity of the enzyme, while the presence of Cu2+ had a negative effect. Thin-layer chromatography analysis demonstrated that P. elgii TKU051 chitosanase exhibited an endo-type cleavage pattern and hydrolyzed chitosan with 98% degree of deacetylation to yield (GlcN)2 and (GlcN)3. The enzymatic properties of P. elgii TKU051 chitosanase render it a promising candidate for application in the production of COS.

Biochemical characterization of a novel bifunctional chitosanase from Paenibacillus barengoltzii for chitooligosaccharide production

A novel chitosanase gene, designated as PbCsn8, was cloned from Paenibacillus barengoltzii. It shared the highest identity of 73% with the glycoside hydrolase (GH) family 8 chitosanase from Bacillus thuringiensis JAM-GG01. The gene was heterologously expressed in Bacillus subtilis as an extracellular protein, and the highest chitosanase yield of 1, 108 U/mL was obtained by high-cell density fermentation in a 5-L fermentor. The recombinant chitosanase (PbCsn8) was purified to homogeneity and biochemically characterized. PbCsn8 was most active at pH 5.5 and 70 °C, respectively. It was stable in a wide pH range of 5.0-11.0 and up to 55 °C. PbCsn8 was a bifunctional enzyme, exhibiting both chitosanase and glucanase activities, with the highest specificity towards chitosan (360 U/mg), followed by barley β-glucan (72 U/mg) and lichenan (13 U/mg). It hydrolyzed chitosan to release mainly chitooligosaccharides (COSs) with degree of polymerization (DP) 2-3, while hydrolyzed barley β-glucan to yield mainly glucooligosaccharides with DP > 5. PbCsn8 was further applied in COS production, and the highest COS yield of 79.3% (w/w) was obtained. This is the first report on a GH family 8 chitosanase from P. barengoltzii. The high yield and remarkable hydrolysis properties may make PbCsn8 a good candidate in industrial application.

Bioprocessing of Squid Pens Waste into Chitosanase by Paenibacillus sp. TKU047 and Its Application in Low-Molecular Weight Chitosan Oligosaccharides Production

Chitosan oligosaccharide (COS) has become of great interest in recent years because of its worthy biological activities. This study aims to produce COS using the enzymatic method, and investigates Paenibacillus sp. TKU047, a chitinolytic-producing strain, in terms of its chitosanase productivity on several chitinous material-containing mediums from fishery process wastes. The highest amount of chitosanase was produced on the medium using 2% (w/v) squid pens powder (0.60 U/mL) as the single carbon and nitrogen (C/N) source. The molecular mass of TKU047 chitosanase, which could be the smallest one among chitinases/chitosanases from the Paenibacillus genus, was approximately 23 kDa according to the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) method. TKU047 chitosanase possessed the highest activity at 60 °C, pH 7, and toward chitosan solution with a higher degree of deacetylation (DDA) value. Additionally, the hydrolysis products of 98% DDA chitosan catalyzed by TKU047 chitosanase showed the degree of polymerization (DP) ranging from 2 to 9, suggesting that it was an endo-type activity chitosanase. The free radical scavenging activity of the obtained chitosan oligosaccharide (COS) was determined. The result showed that COS produced with Paenibacillus sp. TKU047 chitosanase expressed a higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity than that from the commercial COSs with maximum activity and IC₅₀ values of 81.20% and 1.02 mg/mL; 18.63% and 15.37 mg/mL; and 15.96% and 15.16 mg/mL, respectively. As such, Paenibacillus sp. TKU047 may have potential use in converting squid pens waste to produce chitosanase as an enzyme for bio-activity COS preparation.

Production of a Thermostable Chitosanase from Shrimp Heads via Paenibacillus mucilaginosus TKU032 Conversion and its Application in the Preparation of Bioactive Chitosan Oligosaccharides

Chitosanase has attracted great attention due to its potential applications in medicine, agriculture, and nutraceuticals. In this study, P. mucilaginosus TKU032, a bacterial strain isolated from Taiwanese soil, exhibited the highest chitosanase activity (0.53 U/mL) on medium containing shrimp heads as the sole carbon and nitrogen (C/N) source. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, a chitosanase isolated from P. mucilaginosus TKU032 cultured on shrimp head medium was determined at approximately 59 kDa. The characterized chitosanase showed interesting properties with optimal temperature and thermal stability up to 70 °C. Three chitosan oligosaccharide (COS) fractions were isolated from hydrolyzed colloidal chitosan that was catalyzed by TKU032 chitosanase. Of these, fraction I showed the highest α-glucosidase inhibitor (aGI) activity (65.86% at 20 mg/mL); its inhibitory mechanism followed the mixed noncompetitive inhibition model. Fractions II and III exhibited strong 2,2-diphenyl1-picrylhydrazyl (DPPH) radical scavenging activity (79.00% at 12 mg/mL and 73.29% at 16 mg/mL, respectively). In summary, the COS fractions obtained by hydrolyzing colloidal chitosan with TKU032 chitosanase may have potential use in medical or nutraceutical fields due to their aGI and antioxidant activities.

Reclamation of Marine Chitinous Materials for Chitosanase Production via Microbial Conversion by Paenibacillus macerans

Chitinous materials from marine byproducts elicit great interest among biotechnologists for their potential biomedical or agricultural applications. In this study, four kinds of marine chitinous materials (squid pens, shrimp heads, demineralized shrimp shells, and demineralized crab shells) were used to screen the best source for producing chitosanase by Paenibacillus macerans TKU029. Among them, the chitosanase activity was found to be highest in the culture using the medium containing squid pens as the sole carbon/nitrogen (C/N) source. A chitosanase which showed molecular weights at 63 kDa was isolated from P. macerans cultured on a squid pens medium. The purified TKU029 chitosanase exhibited optimum activity at 60 °C and pH 7, and was stable at temperatures under 50 °C and pH 3-8. An analysis by MALDI-TOF MS revealed that the chitosan oligosaccharides (COS) obtained from the hydrolysis of water-soluble chitosan by TKU029 crude enzyme showed various degrees of polymerization (DP), varying from 3⁻6. The obtained COS enhanced the growth of four lactic acid bacteria strains but exhibited no effect on the growth of E. coli. By specialized growth enhancing effects, the COS produced from hydrolyzing water soluble chitosan with TKU029 chitinolytic enzymes could have potential for use in medicine or nutraceuticals.

Conversion of Squid Pens to Chitosanases and Proteases via Paenibacillus sp. TKU042

Chitosanases and proteases have received much attention due to their wide range of applications. Four kinds of chitinous materials, squid pens, shrimp heads, demineralized shrimp shells and demineralized crab shells, were used as the sole carbon and nitrogen (C/N) source to produce chitosanases, proteases and α-glucosidase inhibitors (αGI) by four different strains of Paenibacillus. Chitosanase productivity was highest in the culture supernatants using squid pens as the sole C/N source. The maximum chitosanase activity of fermented squid pens (0.759 U/mL) was compared to that of fermented shrimp heads (0.397 U/mL), demineralized shrimp shells (0.201 U/mL) and demineralized crab shells (0.216 U/mL). A squid pen concentration of 0.5% was suitable for chitosanase, protease and αGI production via Paenibacillus sp. TKU042. Multi-purification, including ethanol precipitation and column chromatography of Macro-Prep High S as well as Macro-Prep DEAE (diethylaminoethyl), led to the isolation of Paenibacillus sp. TKU042 chitosanase and protease with molecular weights of 70 and 35 kDa, respectively. For comparison, 16 chitinolytic bacteria, including strains of Paenibacillus, were investigated for the production of chitinase, exochitinase, chitosanase, protease and αGI using two kinds of chitinous sources.

Interaction between chitosan and its related enzymes: A review

Chitosan-related enzymes including chitosanases, exo-β-glucosaminidases, and enzymes having chitosan-binding modules recognize ligands through electrostatic interactions between the acidic amino acids in proteins and amino groups of chitosan polysaccharides. However, in GH8 chitosanases, several aromatic residues are also involved in substrate recognition through stacking interactions, and these enzymes consequently hydrolyze β-1,4-glucan as well as chitosan. The binding grooves of these chitosanases are extended and opened at both ends of the grooves, so that the enzymes can clamp a long chitosan polysaccharide. The association/dissociation of positively charged glucosamine residues to/from the binding pocket of a GH2 exo-β-glucosaminidase controls the p K_a of the catalytic acid, thereby maintaining the high catalytic potency of the enzyme. In contrast to chitosanases, chitosan-binding modules only accommodate a couple of glucosamine residues, predominantly recognizing the non-reducing end glucosamine residue of chitosan by electrostatic interactions and a hydrogen-bonding network. These structural findings on chitosan-related enzymes may contribute to future applications for the efficient conversion of the chitin/chitosan biomass.

Recent Progress in Chitosanase Production of Monomer-Free Chitooligosaccharides: Bioprocess Strategies and Future Applications

Biological activities of chitosan oligosaccharides (COS) are well documented, and numerous reports of COS production using specific and non-specific enzymes are available. However, strategies for improving the overall yield by making it monomer free need to be developed. Continuous enzymatic production from chitosan derived from marine wastes is desirable and is cost-effective. Isolation of potential microbes showing chitosanase activity from various ecological niches, gene cloning, enzyme immobilization, and fractionation/purification of COS are some areas, where lot of work is in progress. This review covers recent measures to improve monomer-free COS production using chitosanase/non-specific enzymes and purification/fractionation of these molecules using ultrafiltration and column chromatographic techniques. Various bioprocess strategies, gene cloning for enhanced chitosanase enzyme production, and other measures for COS yield improvements have also been covered in this review. COS derivative preparation as well as COS-coated nanoparticles for efficient drug delivery are being focused in recent studies.

Mechanism of chitosan recognition by CBM32 carbohydrate-binding modules from a Paenibacillus sp. IK-5 chitosanase/glucanase

An antifungal chitosanase/glucanase isolated from the soil bacterium Paenibacillus sp. IK-5 has two CBM32 chitosan-binding modules (DD1 and DD2) linked in tandem at the C-terminus. In order to obtain insights into the mechanism of chitosan recognition, the structures of DD1 and DD2 were solved by NMR spectroscopy and crystallography. DD1 and DD2 both adopted a β-sandwich fold with several loops in solution as well as in crystals. On the basis of chemical shift perturbations in 1H-15N-HSQC resonances, the chitosan tetramer (GlcN)4 was found to bind to the loop region extruded from the core β-sandwich of DD1 and DD2. The binding site defined by NMR in solution was consistent with the crystal structure of DD2 in complex with (GlcN)3, in which the bound (GlcN)3 stood upright on its non-reducing end at the binding site. Glu14 of DD2 appeared to make an electrostatic interaction with the amino group of the non-reducing end GlcN, and Arg31, Tyr36 and Glu61 formed several hydrogen bonds predominantly with the non-reducing end GlcN. No interaction was detected with the reducing end GlcN. Since Tyr36 of DD2 is replaced by glutamic acid in DD1, the mutation of Tyr36 to glutamic acid was conducted in DD2 (DD2-Y36E), and the reverse mutation was conducted in DD1 (DD1-E36Y). Ligand-binding experiments using the mutant proteins revealed that this substitution of the 36th amino acid differentiates the binding properties of DD1 and DD2, probably enhancing total affinity of the chitosanase/glucanase toward the fungal cell wall.

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.

Evaluation of chitosan-binding amino acid residues of chitosanase from Paenibacillus fukuinensis

Chitosan oligosaccharides longer than a hexamer have higher bioactivity than polymer or shorter oligosaccharides, such as the monomer or dimer. In our previous work, we generated Paenibacillus fukuinensis chitosanase-displaying yeast using yeast cell surface displaying system and demonstrated the catalytic base. Here we investigated the specific function of putative four amino acid residues Trp159, Trp228, Tyr311, and Phe406 engaged in substrate binding. Using this system, we generated chitosanase mutants in which the four amino acid residues were substituted with Ala and the chitosanase activity assay and HPLC analysis were performed. Based on these results, we demonstrated that Trp159 and Phe406 were critical for hydrolyzing both polymer and oligosaccharide, and Trp228 and Tyr311 were especially important for binding to oligosaccharide, such as the chitosan-hexamer, not to the chitosan polymer. From the results, we suggested the possibility of the effective strategy for designing useful mutants that produce chitosan oligosaccharides holding higher bioactivity.

Cooperative degradation of chitin by extracellular and cell surface-expressed chitinases from Paenibacillus sp. strain FPU-7

Chitin, a major component of fungal cell walls and invertebrate cuticles, is an exceedingly abundant polysaccharide, ranking next to cellulose. Industrial demand for chitin and its degradation products as raw materials for fine chemical products is increasing. A bacterium with high chitin-decomposing activity, Paenibacillus sp. strain FPU-7, was isolated from soil by using a screening medium containing α-chitin powder. Although FPU-7 secreted several extracellular chitinases and thoroughly digested the powder, the extracellular fluid alone broke them down incompletely. Based on expression cloning and phylogenetic analysis, at least seven family 18 chitinase genes were found in the FPU-7 genome. Interestingly, the product of only one gene (chiW) was identified as possessing three S-layer homology (SLH) domains and two glycosyl hydrolase family 18 catalytic domains. Since SLH domains are known to function as anchors to the Gram-positive bacterial cell surface, ChiW was suggested to be a novel multimodular surface-expressed enzyme and to play an important role in the complete degradation of chitin. Indeed, the ChiW protein was localized on the cell surface. Each of the seven chitinase genes (chiA to chiF and chiW) was cloned and expressed in Escherichia coli cells for biochemical characterization of their products. In particular, ChiE and ChiW showed high activity for insoluble chitin. The high chitinolytic activity of strain FPU-7 and the chitinases may be useful for environmentally friendly processing of chitin in the manufacture of food and/or medicine.

The first identification of carbohydrate binding modules specific to chitosan

Two carbohydrate binding modules (DD1 and DD2) belonging to CBM32 are located at the C terminus of a chitosanase from Paenibacillus sp. IK-5. We produced three proteins, DD1, DD2, and tandem DD1/DD2 (DD1+DD2), and characterized their binding ability. Transition temperature of thermal unfolding (Tm) of each protein was elevated by the addition of cello-, laminari-, chitin-, or chitosan-hexamer (GlcN)6. The Tm elevation (ΔTm) in DD1 was the highest (10.3 °C) upon the addition of (GlcN)6 and was markedly higher than that in DD2 (1.0 °C). A synergistic effect was observed (ΔTm = 13.6 °C), when (GlcN)6 was added to DD1+DD2. From isothermal titration calorimetry experiments, affinities to DD1 were not clearly dependent upon chain length of (GlcN)n; ΔGr° values were -7.8 (n = 6), -7.6 (n = 5), -7.6 (n = 4), -7.6 (n = 3), and -7.1 (n = 2) kcal/mol, and the value was not obtained for GlcN due to the lowest affinity. DD2 bound (GlcN)n with the lower affinities (ΔGr° = -5.0 (n = 3) ~ -5.2 (n = 6) kcal/mol). Isothermal titration calorimetry profiles obtained for DD1+DD2 exhibited a better fit when the two-site model was used for analysis and provided greater affinities to (GlcN)6 for individual DD1 and DD2 sites (ΔGr° = -8.6 and -6.4 kcal/mol, respectively). From NMR titration experiments, (GlcN)n (n = 2~6) were found to bind to loops extruded from the core β-sandwich of individual DD1 and DD2, and the interaction sites were similar to each other. Taken together, DD1+DD2 is specific to chitosan, and individual modules synergistically interact with at least two GlcN units, facilitating chitosan hydrolysis.

Cloning and overexpression of a new chitosanase gene from Penicillium sp. D-1

A chitosanase gene, csn, was cloned from Penicillium sp. D-1 by inverse PCR. The cDNA sequence analysis revealed that csn had no intron. The deduced CSN protein consists of 250 amino acids including a 20-amino acid signal peptide, and shared 83.6% identity with the family 75 chitosanase from Talaromyces stipitatus (B8M2R4). The mature protein was overexpressed in Escherichia coli and purified with the affinity chromatography of Ni²⁺-NTA. The novel recombinant chitosanase showed maximal catalytic activity at pH 4.0 and 48°C. Moreover, the activity of CSN was stable over a broad pH range of 3.0-8.0, and the enzymatic activity was significantly enhanced by Mg²⁺ and Mn²⁺. The CSN could effectively hydrolyze colloidal chitosan and chitosan, while could not hydrolyze chitin and carboxymethylcellulose (CMC). Due to the particular acidophily, CSN has the potential application in the recycling of chitosan wastes.

The GenBank/EMBL/DDBJ accession numbers for the 18S rRNA gene and chitosanase gene of strain D-1 are JF950269 and JF950270, respectively.

Modification of genetic regulation of a heterologous chitosanase gene in Streptomyces lividans TK24 leads to chitosanase production in the absence of chitosan

BACKGROUND

Chitosanases are enzymes hydrolysing chitosan, a β-1,4 linked D-glucosamine bio-polymer. Chitosan oligosaccharides have numerous emerging applications and chitosanases can be used for industrial enzymatic hydrolysis of chitosan. These extracellular enzymes, produced by many organisms including fungi and bacteria, are well studied at the biochemical and enzymatic level but very few works were dedicated to the regulation of their gene expression. This is the first study on the genetic regulation of a heterologous chitosanase gene (csnN106) in Streptomyces lividans.

RESULTS

Two S. lividans strains were used for induction experiments: the wild type strain and its mutant (ΔcsnR), harbouring an in-frame deletion of the csnR gene, encoding a negative transcriptional regulator. Comparison of chitosanase levels in various media indicated that CsnR regulates negatively the expression of the heterologous chitosanase gene csnN106. Using the ΔcsnR host and a mutated csnN106 gene with a modified transcription operator, substantial levels of chitosanase could be produced in the absence of chitosan, using inexpensive medium components. Furthermore, chitosanase production was of higher quality as lower levels of extracellular protease and protein contaminants were observed.

CONCLUSIONS

This new chitosanase production system is of interest for biotechnology as only common media components are used and enzyme of high degree of purity is obtained directly in the culture supernatant.

Identification, characterization, and regulation of a novel antifungal chitosanase gene (cho) in Anabaena spp

Two contrasting cyanobacterial species (Anabaena fertilissima and Anabaena sphaerica) were selected based on differences in antifungal behavior in order to study the mechanism for production of an antifungal enzyme and the genes responsible for this production. In A. fertilissima, chitosanase and antifungal activities were increased significantly under of growth-limiting conditions (8 of light and 16 h of darkness). The lack of such activities in A. sphaerica was associated with high levels of protein that accumulated during the stationary phase (at 28 days) under the same light conditions. The gene putatively responsible for chitosanase and antifungal activities was amplified using specific primers, and sequence analysis of the amplified products (1.086 and 1.101 kb in A. sphaerica and A. fertilissima, respectively) showed that they belong to the glycoside hydrolase 3 (GH3)-like family of Anabaena variabilis ATCC 29413. Pairwise alignment of the corresponding protein sequences identified a putative signal peptide (amino acids 1 to 23) and some amino acid changes in the sequence of A. fertilissima which may be responsible for functioning of the chitosanase and the observed antifungal activity. Hydrolysis of the chitosan oligosaccharide (GlcN)(5) to (GlcN)(2) and (GlcN)(3) confirmed the presence of chitosanase activity in A. fertilissima. Site-directed mutagenesis of the A. fertilissima chitosanase-encoding gene (cho) led to identification of catalytic residues (Glu-121 and Glu-141) important for the antifungal effect of the cho product. The level of expression of cho was monitored by quantitative real-time reverse transcription-PCR, which indicated that transcription of this gene is significantly enhanced under conditions that retard growth, such as a long dark period.

Functional analysis of conserved aromatic amino acids in the discoidin domain of Paenibacillus beta-1,3-glucanase

The 190-kDa Paenibacillus beta-1,3-glucanase (LamA) contains a catalytic module of the glycoside hydrolase family 16 (GH16) and several auxiliary domains. Of these, a discoidin domain (DS domain), present in both eukaryotic and prokaryotic proteins with a wide variety of functions, exists at the carboxyl-terminus. To better understand the bacterial DS domain in terms of its structure and function, this domain alone was expressed in Escherichia coli and characterized. The results indicate that the DS domain binds various polysaccharides and enhances the biological activity of the GH16 module on composite substrates. We also investigated the importance of several conserved aromatic residues in the domain's stability and substrate-binding affinity. Both were affected by mutations of these residues; however, the effect on protein stability was more notable. In particular, the forces contributed by a sandwiched triad (W1688, R1756, and W1729) were critical for the presumable beta-sandwich fold.

Cloning of two cellulase genes from endophytic Paenibacillus polymyxa GS01 and comparison with cel 44C-man 26A

Endophytic bacteria are acknowledged as a new source of genes, proteins and other biochemical compounds, which are often used in biochemical processes. In this study, Paenibacillus polymyxa GS01 was isolated from the interior of the roots of Korean cultivars of ginseng (Panax ginseng C. A. Meyer). Two cellulase genes, cel 5A and cel 5B, were cloned from GS01, and encode 334 aa and 573 aa proteins, respectively. Cel5A and Cel5B each contain a glycosyl hydrolase family 5 (GH5) catalytic domain. The molecular mass of Cel5A and Cel5B were estimated to be 33 kDa and 61 kDa, respectively, by CMC-SDS-PAGE. When purified from Escherichia coli Cel5A and Cel5B both displayed cellulase activity with pH optima of 7.0 and 6.0, respectively and shared a temperature optimum of 50 degrees C. Neither enzyme had detectable xylanase, lichenase, or mannase activity, in contrast to the multifunctional Cel44C-Man26A enzyme of P. polymyxa which displays cellulase, xylanase, lichenase and mannanase activities. However, Cel5A and Cel5B exhibited higher specific cellulase activity than Cel44C-Man26A (120% and 140%, respectively). Cel5A and Cel5B mutants with alanine substitutions at a conserved glutamic acid in the GH5 domain (Glu 179 of Cel5A and Glu184 of Cel5B) lacked cellulase activity, suggesting that this residue is important for GH5 domain function.

Chitosan and its antimicrobial potential--a critical literature survey

Chitosan, an aminopolysaccharide biopolymer, has a unique chemical structure as a linear polycation with a high charge density, reactive hydroxyl and amino groups as well as extensive hydrogen bonding. It displays excellent biocompatibility, physical stability and processability. The term 'chitosan' describes a heterogeneous group of polymers combining a group of physicochemical and biological characteristics, which allow for a wide scope of applications that are both fascinating and as yet uncharted. The increased awareness of the potentials and industrial value of this biopolymer lead to its utilization in many applications of technical interest, and increasingly in the biomedical arena. Although not primarily used as an antimicrobial agent, its utility as an ingredient in both food and pharmaceutical formulations lately gained more interest, when a scientific understanding of at least some of the pharmacological activities of this versatile carbohydrate began to evolve. However, understanding the various factors that affect its antimicrobial activity has become a key issue for a better usage and a more efficient optimization of chitosan formulations. Moreover, the use of chitosan in antimicrobial systems should be based on sufficient knowledge of the complex mechanisms of its antimicrobial mode of action, which in turn would help to arrive at an appreciation of its entire antimicrobial potential.

Advance in chitosan hydrolysis by non-specific cellulases

Besides the specific chitinase, chitosanase and lysozyme, chitosan also could be hydrolyzed by some non-specific enzymes such as cellulase, protease, lipase and pepsin, especially cellulase, which show high activity on chitosan. Almost all the cellulases produced by different kinds of microorganisms could degrade chitosan to chitooligomers. The existence of bifunctional enzymes with cellulase and chitosanase activity is one of the reasons for cellulase on chitosan hydrolysis. The bifunctional cellulase-chitosanases mainly belong to glycoside hydrolase family 8 (GH-8), few belong to GH-5 and GH-7, according to the homogeneity analysis of amino acids sequences. Their three dimensional structures however have not been clearly determined. This paper may serve as a guide for a further study on the relationship between structure and function of chitosanolytic cellulases.

Cloning and functional characterization of a complex endo-beta-1,3-glucanase from Paenibacillus sp

A beta-1,3-glucanase gene, encoding a protein of 1,793 amino acids, was cloned from a strain of Paenibacillus sp. in this study. This large protein, designated as LamA, consists of many putative functional units, which include, from N to C terminus, a leader peptide, three repeats of the S-layer homologous module, a catalytic module of glycoside hydrolase family 16, four repeats of the carbohydrate-binding module of family CBM_4_9, and an analogue of coagulation factor Fa5/8C. Several truncated proteins, composed of the catalytic module with various organizations of the appended modules, were successfully expressed and characterized in this study. Data indicated that the catalytic module specifically hydrolyze beta-1,3- and beta-1,3-1,4-glucans. Also, laminaritriose was the major product upon endolytic hydrolysis of laminarin. The CBM repeats and Fa5/8C analogue substantially enhanced the hydrolyzing activity of the catalytic module, particularly toward insoluble complex substrates, suggesting their modulating functions in the enzymatic activity of LamA. Carbohydrate-binding assay confirmed the binding capabilities of the CBM repeats and Fa5/8C analogue to beta-1,3-, beta-1,3-1,4-, and even beta-1,4-glucans. These appended modules also enhanced the inhibition effect of the catalytic module on the growth of Candida albicans and Rhizoctonia solani.

Yeast cell-surface expression of chitosanase from Paenibacillus fukuinensis

To produce chitoorigosaccharides using chitosan, we attempted to construct Paenibacillus fukuinensis chitosanase-displaying yeast cells as a whole-cell biocatalyst through yeast cell-surface engineering. The localization of the chitosanase on the yeast cell surface was confirmed by immunofluorescence labeling of cells. The chitosanase activity of the constructed yeast was investigated by halo assay and the dinitrosalicylic acid method.

Mutanase from a Paenibacillus isolate: Nucleotide sequence of the gene and properties of recombinant enzymes

A mutanase (alpha-1,3-glucanase)-producing microorganism was isolated from a soil sample and was identified as a relative of Paenibacillus sp. The mutanase was purified to homogeneity from culture, and its molecular mass was around 57 kDa. The gene for the mutanase was cloned by PCR using primers based on the N-terminal amino acid sequence of the purified enzyme. The determined nucleotide sequence of the gene consisted of 3651-bp open reading frame that encoded a predicted 1217-amino acid polypeptide including a 43-amino acid signal peptide. The mature enzyme showed similarity to mutanases RM1 of Bacillus sp. strain RM1 and KA-304 of Bacillus circulans with 65.6% and 62.7% identity, respectively. The predicted molecular mass of the mutanase was 123 kDa. Thus, the enzyme purified from the isolate appears to be truncated by proteolysis. The genes for the full-length and truncated mutanases were expressed in Bacillus subtilis cells, and the corresponding recombinant enzymes were purified to homogeneity. The molecular masses of the two enzymes were 116 and 57 kDa, respectively. The specific activity was 10-fold higher for the full-length enzyme than for the truncated enzyme. The optimal pH and temperature for both recombinant enzymes was pH 6.4 in citrate buffer and 45 degrees C to 50 degrees C. Amongst several tested polysaccharides, the recombinant full-length enzyme specifically hydrolyzed mutan.

A cel44C-man26A gene of endophytic Paenibacillus polymyxa GS01 has multi-glycosyl hydrolases in two catalytic domains

A bacterial strain Paenibacillus polymyxa GS01 was isolated from the interior of the roots of Korean cultivars of ginseng (Panax ginseng C. A. Meyer). The cel44C-man26A gene was cloned from this endophytic strain. This 4,056-bp gene encodes for a 1,352-aa protein which, based on BLAST search homologies, contains a glycosyl hydrolase family 44 (GH44) catalytic domain, a fibronectin domain type 3, a glycosyl hydrolase family 26 (GH26) catalytic domain, and a cellulose-binding module type 3. The multifunctional enzyme domain GH44 possesses cellulase, xylanase, and lichenase activities, while the enzyme domain GH26 possesses mannanase activity. The Cel44C enzyme expressed in and purified from Escherichia coli has an optimum pH of 7.0 for cellulase and lichenase activities, but is at an optimum pH of 5.0 for xylanase and mannanase activities. The optimum temperature for enzymatic activity was 50 degrees C for all substrates. No detectable enzymatic activity was detected for the Cel44C-Man26A mutants E91A and E222A. These results suggest that the amino acid residues Glu(91) and Glu(222) may play an important role in the glycosyl hydrolases activity of Cel44C-Man26A.

Analysis of essential carboxylic amino acid residues for catalytic activity of fungal chitosanases by site-directed mutagenesis

A comparison of amino acid sequences of fungal chitosanases, belonging to family 75 of glycosyl hydrolases, revealed three carboxylic amino acid residues completely conserved among all of the chitosanases. To study the role of these residues in catalysis, they were replaced with other residues by site-directed mutagenesis in the chitosanase gene of Fusarium solani. The mutated genes were expressed in the yeast Saccharomyces cerevisiae and the resulting recombinant chitosanases were used in kinetic analysis. Chitosanases with Asp-175-->Asn and Glu-188-->Gln mutations were essentially inactive, whereas those with Asp-175-->Glu and Glu-188-->Asp mutations retained 25-50% specific activity as compared with the wild-type enzyme. The mutation of Asp-212-->Asn did not decrease specific activity to a large extent. Circular dichroism analysis confirmed that the mutant chitosanases had similar secondary structures to that of the wild-type enzyme. These results indicate that Asp-175 and Glu-188 are essential residues for the catalytic activity of chitosanase. Time-dependent (1)H-NMR analysis for the hydrolysis of D-glucosamine hexamer revealed that a fungal chitosanase is an inverting enzyme producing only the alpha anomeric form of reaction products.

New chitosan-degrading strains that produce chitosanases similar to ChoA of Mitsuaria chitosanitabida

The betaproteobacterium Mitsuaria chitosanitabida (formerly Matsuebacter chitosanotabidus) 3001 produces a chitosanase (ChoA) that is classified in glycosyl hydrolase family 80. While many chitosanase genes have been isolated from various bacteria to date, they show limited homology to the M. chitosanitabida 3001 chitosanase gene (choA). To investigate the phylogenetic distribution of chitosanases analogous to ChoA in nature, we identified 67 chitosan-degrading strains by screening and investigated their physiological and biological characteristics. We then searched for similarities to ChoA by Western blotting and Southern hybridization and selected 11 strains whose chitosanases showed the most similarity to ChoA. PCR amplification and sequencing of the chitosanase genes from these strains revealed high deduced amino acid sequence similarities to ChoA ranging from 77% to 99%. Analysis of the 16S rRNA gene sequences of the 11 selected strains indicated that they are widely distributed in the beta and gamma subclasses of Proteobacteria and the Flavobacterium group. These observations suggest that the ChoA-like chitosanases that belong to family 80 occur widely in a broad variety of bacteria.

Molecular characterization of NADase-streptolysin O operon of hemolytic streptococci

Whether slo, the gene encoding streptolysin O (SLO), a streptococcal cytolysin, has its own promoter or not is unsettled as yet. Present analyses demonstrate that slo is a member of an operon covering the upper-stream nusG and nga (NADase) genes, from which transcription of slo proceeds polycistronically, and major transcript is produced by readthrough from nga promoter. Mutational conversion of the sixth nucleotide T at the putative -10 region of chromosomal nga gene into C caused a drastic decrease in both NADase and SLO activities and the disappearance of the two corresponding mRNA bands from the Northern blot profile. The initiation site of the transcription was determined at 56 bp upstream (NusG gene) and 25 bp upstream (NADase gene) of each initiation codon. Although the promoter region of slo gene is highly conserved between group A and C streptococci, the proper slo promoter is nonfunctional in group C strain H46A. Moreover, commonly conserved arrangement was limited to the nusG-nga-orf1-slo region. These results indicate an intimate relationship between NADase and SLO in the regulation of their biosynthesis. Additional results suggest that NADase, synthesized as precursor with feeble activity, is activated by removing the carboxyl terminal region during or after secretion into culture medium.

Purification of a constitutive chitosanase produced byBacillussp. MET 1299 with cloning and expression of the gene

A chitosanase produced constitutively by Bacillus sp. MET 1299 was purified by SP-Sephadex column chromatography. The molecular weight was estimated to be 52 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Optimal enzyme activity was observed at a pH of 5.5 and temperature of 60 degrees C. The purified chitosanase showed high activity on 90% deacetylated colloidal chitosan and beta-glucan, but not on hydrolyzed colloidal chitin, CMC, or their derivatives. The N-terminal amino acid sequence of the enzyme was determined. The cloned full length gene, 1362 bp in size, encoded a single peptide of 453 amino acids and had a conserved amino acid sequence of glycosyl hydrolase family 8. A search of the cDNA sequence with NCBI BLAST showed homology with chitosanase of Bacillus sp. KTCC 0377BP and Bacillus sp. No. 7-M. The recombinant protein was expressed in Escherichia coli, purified using affinity chromatography and characterized.

Purification and characterization of chitosanase from Bacillus sp. strain KCTC 0377BP and its application for the production of chitosan oligosaccharides

For the enzymatic production of chitosan oligosaccharides from chitosan, a chitosanase-producing bacterium, Bacillus sp. strain KCTC 0377BP, was isolated from soil. The bacterium constitutively produced chitosanase in a culture medium without chitosan as an inducer. The production of chitosanase was increased from 1.2 U/ml in a minimal chitosan medium to 100 U/ml by optimizing the culture conditions. The chitosanase was purified from a culture supernatant by using CM-Toyopearl column chromatography and a Superose 12HR column for fast-performance liquid chromatography and was characterized according to its enzyme properties. The molecular mass of the enzyme was estimated to be 45 kDa by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme demonstrated bifunctional chitosanase-glucanase activities, although it showed very low glucanase activity, with less than 3% of the chitosanase activity. Activity of the enzyme increased with an increase of the degrees of deacetylation (DDA) of the chitosan substrate. However, the enzyme still retained 72% of its relative activity toward the 39% DDA of chitosan, compared with the activity of the 94% DDA of chitosan. The enzyme produced chitosan oligosaccharides from chitosan, ranging mainly from chitotriose to chitooctaose. By controlling the reaction time and by monitoring the reaction products with gel filtration high-performance liquid chromatography, chitosan oligosaccharides with a desired oligosaccharide content and composition were obtained. In addition, the enzyme was efficiently used for the production of low-molecular-weight chitosan and highly acetylated chitosan oligosaccharides. A gene (csn45) encoding chitosanase was cloned, sequenced, and compared with other functionally related genes. The deduced amino acid sequence of csn45 was dissimilar to those of the classical chitosanase belonging to glycoside hydrolase family 46 but was similar to glucanases classified with glycoside hydrolase family 8.