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|Substrate For (Enzyme):||endo-Chitinase|
High purity Tetraacetyl-chitotetraose for use in research, biochemical enzyme assays and in vitro diagnostic analysis.
Prepared from chitin.
Also offers other oligosaccharide products.
Versatile high resolution oligosaccharide microarrays for plant glycobiology and cell wall research.
Pedersen, H. L., Fangel, J. U., McCleary, B., Ruzanski, C., Rydahl, M. G., Ralet, M. C., Farkas, V., Von Schantz, L., Marcus, S. E., Andersen, M.C. F., Field, R., Ohlin, M., Knox, J. P., Clausen, M. H. & Willats, W. G. T. (2012). Journal of Biological Chemistry, 287(47), 39429-39438.
Microarrays are powerful tools for high throughput analysis, and hundreds or thousands of molecular interactions can be assessed simultaneously using very small amounts of analytes. Nucleotide microarrays are well established in plant research, but carbohydrate microarrays are much less established, and one reason for this is a lack of suitable glycans with which to populate arrays. Polysaccharide microarrays are relatively easy to produce because of the ease of immobilizing large polymers noncovalently onto a variety of microarray surfaces, but they lack analytical resolution because polysaccharides often contain multiple distinct carbohydrate substructures. Microarrays of defined oligosaccharides potentially overcome this problem but are harder to produce because oligosaccharides usually require coupling prior to immobilization. We have assembled a library of well characterized plant oligosaccharides produced either by partial hydrolysis from polysaccharides or by de novo chemical synthesis. Once coupled to protein, these neoglycoconjugates are versatile reagents that can be printed as microarrays onto a variety of slide types and membranes. We show that these microarrays are suitable for the high throughput characterization of the recognition capabilities of monoclonal antibodies, carbohydrate-binding modules, and other oligosaccharide-binding proteins of biological significance and also that they have potential for the characterization of carbohydrate-active enzymes.Hide Abstract
Biochemical characterization of a novel acidic chitinase with antifungal activity from Paenibacillus xylanexedens Z2-4.
Zhang, W., Ma, J., Yan, Q., Jiang, Z. & Yang, S. (2021). International Journal of Biological Macromolecules, 182, 1528-1536.
A chitinase gene (PxChi52) from Paenibacillus xylanexedens Z2-4 was cloned and heterologously expressed in Escherichia coli BL21 (DE3). PxChi52 shared the highest identity of 91% with a glycoside hydrolase family 18 chitinase (ChiD) from Bacillus circulans. The recombinant enzyme (PxChi52) was purified and biochemically characterized. PxChi52 had a molecular mass of 52.8 kDa. It was most active at pH 4.5 and 65°C, respectively, and stable in a wide pH range of 4.0-13.0 and up to 50°C. The enzyme exhibited the highest specific activity of 16.0 U/mg towards colloidal chitin, followed by ethylene glycol chitin (5.4 U/mg) and ball milled chitin (0.4 U/mg). The Km and Vmax values of PxChi52 towards colloidal chitin were determined to be 3.06 mg/mL and 71.38 U/mg, respectively, PxChi52 hydrolyzed colloidal chitin and chitooligosaccharides with degree of polymerization 2-5 to release mainly N-acetyl chitobiose. In addition, PxChi52 displayed inhibition effects on the growth of some phytopathogenic fungi, including Alternaria alstroemeriae, Botrytis cinerea, Rhizoctonia solani, Sclerotinia sclerotiorum and Valsa mali. The unique properties of PxChi52 may enable it potential application in agriculture field as a biocontrol agent.Hide Abstract
Chromatographic assays for the enzymatic degradation of chitin.
Mekasha, S., Tuveng, T. R., Vaaje-Kolstad, G. & Eijsink, V. G. (2021). Bio-protocol, 11(9), e4014.
Chitin is an insoluble linear polymer of β(1→4)-linked N-acetylglucosamine. Enzymatic cleavage of chitin chains can be achieved using hydrolytic enzymes, called chitinases, and/or oxidative enzymes, called lytic polysaccharide monooxygenases (LPMOs). These two groups of enzymes have different modes of action and yield different product types that require different analytical methods for detection and quantitation. While soluble chromogenic substrates are readily available for chitinases, proper insight into the activity of these enzymes can only be obtained by measuring activity toward their polymeric, insoluble substrate, chitin. For LPMOs, only assays using insoluble chitin are possible and relevant. Working with insoluble substrates complicates enzyme assays from substrate preparation to product analysis. Here, we describe typical set-ups for chitin degradation reactions and the chromatographic methods used for product analysis. Graphical abstract: Overview of chromatographic methods for assessing the enzymatic degradation of chitin.Hide Abstract
Biochemical characterization of a novel bifunctional chitosanase from Paenibacillus barengoltzii for chitooligosaccharide production.
Jiang, Z., Yan, Q. & Yang, S. (2021). World Journal of Microbiology and Biotechnology, 37(5), 1-13.
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.Hide Abstract
Recent structural insights into the mechanism of lysozyme hydrolysis.
Tanaka, I., Nishinomiya, R., Goto, R., Shimazaki, S. & Chatake, T. (2021). Acta Crystallographica Section D: Structural Biology, 77(3).
Lysozyme hydrolyzes the glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycans located in the bacterial cell wall. The mechanism of the hydrolysis reaction of lysozyme was first studied more than 50 years ago; however, it has not yet been fully elucidated and various mechanisms are still being investigated. One reaction system that has commonly been proposed is that the lysozyme intermediate undergoes covalent ligand binding during hydrolysis. However, these findings resulted from experiments performed under laboratory conditions using fluorine-based ligands, which facilitate the formation of covalent bonds between the ligands and the catalytic side chain of lysozyme. More recently, high-resolution X-ray structural analysis was used to study the complex of lysozyme with an N-acetylglucosamine tetramer. As a result, the carboxyl group of Asp52 was found to form a relatively strong hydrogen-bond network and had difficulty binding covalently to C1 of the carbohydrate ring. To confirm this hydrogen-bond network, neutron test measurements were successfully performed to a resolution of better than 1.9 Å.Hide Abstract
LysM receptor-like kinase LYK9 of Pisum Sativum L. may regulate plant responses to chitooligosaccharides differing in structure.
Leppyanen, I. V., Pavlova, O. A., Vashurina, M. A., Bovin, A. D., Dolgikh, A. V., Shtark, O. Y., Sendersky, I. V., Dolgikh, V. V., Tikhonovich, I. A. & Dolgikh, E. A. (2021). International Journal of Molecular Sciences, 22(2), 711.
This study focused on the interactions of pea (Pisum sativum L.) plants with phytopathogenic and beneficial fungi. Here, we examined whether the lysin-motif (LysM) receptor-like kinase PsLYK9 is directly involved in the perception of long- and short-chain chitooligosaccharides (COs) released after hydrolysis of the cell walls of phytopathogenic fungi and identified in arbuscular mycorrhizal (AM) fungal exudates. The identification and analysis of pea mutants impaired in the lyk9 gene confirmed the involvement of PsLYK9 in symbiosis development with AM fungi. Additionally, PsLYK9 regulated the immune response and resistance to phytopathogenic fungi, suggesting its bifunctional role. The existence of co-receptors may provide explanations for the potential dual role of PsLYK9 in the regulation of interactions with pathogenic and AM fungi. Co-immunoprecipitation assay revealed that PsLYK9 and two proposed co-receptors, PsLYR4 and PsLYR3, can form complexes. Analysis of binding capacity showed that PsLYK9 and PsLYR4, synthesized as extracellular domains in insect cells, were able to bind the deacetylated (DA) oligomers CO5-DA–CO8-DA. Our results suggest that the receptor complex consisting of PsLYK9 and PsLYR4 can trigger a signal pathway that stimulates the immune response in peas. However, PsLYR3 seems not to be involved in the perception of CO4-5, as a possible co-receptor of PsLYK9.Hide Abstract
Biochemical characterization of a bifunctional chitinase/lysozyme from Streptomyces sampsonii suitable for N-acetyl chitobiose production.
Zhang, W., Liu, Y., Ma, J., Yan, Q., Jiang, Z. & Yang, S. (2020). Biotechnology Letters, 1-11.
Chitinases play important role in chitin bioconversion, while few of them have been put into use due to their poor properties. We aimed to identify and characterize chitinases suitable for N-acetyl chitooligosaccharides (COSs) production from chitin materials. A chitinase gene (SsChi28) from Streptomyces sampsonii XY2-7 was cloned and heterologously expressed in E. coli BL21 (DE3) as an active protein. The deduced protein shared high sequence identities and structure similarities with some glycoside hydrolase family 19 chitinases. The recombinant enzyme (SsChi28) was purified and biochemically characterized. SsChi28 was a monomeric protein with a molecular mass of 30 kDa estimated by SDS-PAGE. It was most active at pH 6.0 and 55°C, respectively, and stable in a wide pH range of 3.5-11.5 and up to 60°C. The enzyme exhibited strict substrate specificities towards ethylene glycol chitin (222.3 U/mg) and colloidal chitin (20.1 U/mg). Besides, it displayed lysozyme activity against Micrococcus lysodeikticus. SsChi28 hydrolyzed colloidal chitin to yield mainly N-acetyl chitobiose, accounting high up to 73% (w/w) in total products. The excellent enzymatic properties of SsChi28 may make it potential in chitin bioconversion (especially for N-acetyl COS production), as well as in biological control of fungal diseases.Hide Abstract
Heterologous expression and characterization of an antifungal chitinase (Chit46) from Trichoderma harzianum GIM 3.442 and its application in colloidal chitin conversion.
Deng, J. J., Shi, D., Mao, H. H., Li, Z. W., Liang, S., Ke, Y. & Luo, X. C. (2019). International Journal of Biological Macromolecules, 134, 113-121.
In this study, a chitinase gene, Chit46 from a mycoparasitic fungus Trichoderma harzianum was successfully expressed in Pichia pastoris with a high heterologous chitinase production of 31.4 U/mL, much higher than the previous reports. The active center and substrate binding pocket of the recombinant Chit46 (rChit46) were analyzed and the effects of pH, temperature, metal ions and glycosylation on its activity were tested. rChit46 effectively hydrolyzed colloidal chitin with a high conversion rate of 80.5% in 3 h and the chitin hydrolysates were mainly composed of (GlcNAc)2 (94.8%), which make it a good candidate for the green recycling of chitinous waste. rChit46 could also significantly inhibit growth of the phytopathogenic fungus Botrytis cinerea, which endowed it with the potential as a biocontrol agent.Hide Abstract
An actinobacteria lytic polysaccharide monooxygenase acts on both cellulose and xylan to boost biomass saccharification.
Corrêa, T. L. R., Júnior, A. T., Wolf, L. D., Buckeridge, M. S., dos Santos, L. V. & Murakami, M. T. (2019). Biotechnology for Biofuels, 12(1), 117.
Background: Lytic polysaccharide monooxygenases (LPMOs) opened a new horizon for biomass deconstruction. They use a redox mechanism not yet fully understood and the range of substrates initially envisaged to be the crystalline polysaccharides is steadily expanding to non-crystalline ones. Results: The enzyme KpLPMO10A from the actinomycete Kitasatospora papulosa was cloned and overexpressed in Escherichia coli cells in the functional form with native N-terminal. The enzyme can release oxidized species from chitin (C1-type oxidation) and cellulose (C1/C4-type oxidation) similarly to other AA10 members from clade II (subclade A). Interestingly, KpLPMO10A also cleaves isolated xylan (not complexed with cellulose, C4-type oxidation), a rare activity among LPMOs not described yet for the AA10 family. The synergistic effect of KpLPMO10A with Celluclast ® and an endo-β-1,4-xylanase also supports this finding. The crystallographic elucidation of KpLPMO10A at 1.6 Å resolution along with extensive structural analyses did not indicate any evident diference with other characterized AA10 LPMOs at the catalytic interface, tempting us to suggest that these enzymes might also be active on xylan or that the ability to attack both crystalline and non-crystalline substrates involves yet obscure mechanisms of substrate recognition and binding. Conclusions: This work expands the spectrum of substrates recognized by AA10 family, opening a new perspective for the understanding of the synergistic efect of these enzymes with canonical glycoside hydrolases to deconstruct ligno(hemi)cellulosic biomass.Hide Abstract
Comparative biocontrol ability of chitinases from bacteria and recombinant chitinases from the thermophilic fungus Thermomyces lanuginosus.
Okongo, R. N., Puri, A. K., Wang, Z., Singh, S. & Permaul, K. (2019). Journal of Bioscience and Bioengineering, 127(6), 663-671.
Microbial chitinases (EC 22.214.171.124) are known to hydrolyse the chitinous gut epithelium of insects and cell walls of many fungi. In this study, seven chitinases from different bacteria and fungi were produced, characterized and their biocontrol abilities against graminaceous stem borers Eldana saccharina, Chilo partellus and Sesamia calamistis were assessed. All chitinases were stable over broad ranges of pH and temperature, however, recombinant fungal chitinases were more acid-stable than the bacterial counterparts. Chitinases from the thermophilic filamentous fungi Thermomyces lanuginosus SSBP (Chit1) and from Bacillus licheniformis (Chit lic) caused 70% and 80% mortality, respectively, in second instar larvae of E. saccharina. Six of the seven partially-purified microbial chitinases inhibited Aspergillus niger, A. flavus, A. alliaceus, A. ochraceus, Fusarium verticillioides and Mucor sp. Overall, microbial chitinases show promise as biocontrol agents of fungi and stalk–boring lepidopterans.Hide Abstract
Chitooligosaccharide binding to CIA17 (Coccinia indica agglutinin). Thermodynamic characterization and formation of higher order complexes.
Bobbili, K. B., Singh, B., Narahari, A., Bulusu, G., Surolia, A. & Swamy, M. J. (2019). International Journal of Biological Macromolecules, 137, 774-782.
CIA17 is a PP2-like, homodimeric lectin made up of 17 kDa subunits present in the phloem exudate of ivy gourd (Coccinia indica). Isothermal titration calorimetric (ITC) studies on the interaction of chitooligosaccharides [(GlcNAc)2–6] showed that the dimeric protein has two sugar binding sites which recognize chitotriose with ~70-fold higher affinity than chitobiose, indicating that the binding site is extended in nature. ITC, atomic force microscopic and non-denaturing gel electrophoresis studies revealed that the high-affinity interaction of CIA17 with chitohexaose (Ka = 1.8 × 107 M−1) promotes the formation of protein oligomers. Computational studies involving homology modeling, molecular docking and molecular dynamics simulations on the binding of chitooligosaccharides to CIA17 showed that the protein binding pocket accommodates up to three GlcNAc residues. Interestingly, docking studies with chitohexaose indicated that its two triose units could interact with binding sites on two protein molecules to yield dimeric complexes of the type CIA17-(GlcNAc)6-CIA17, which can extend in length by the binding of additional chitohexaose and CIA17 molecules. These results suggest that PP2 proteins play a role in plant defense against insect/pathogen attack by directly binding with the higher chain length chitooligosaccharides and forming extended, filamentous structures, which facilitate wound sealing.Hide Abstract
Krolicka, M., Hinz, S. W., Koetsier, M. J., Joosten, R., Eggink, G., van den Broek, L. A. & Boeriu, C. G. (2018). Journal of Agricultural and Food Chemistry, 66(7), 1658-1669.
A thermostable chitinase Chi1 from Myceliophthora thermophila C1 was homologously produced and characterized. Chitinase Chi1 shows high thermostability at 40°C (>140 h 90% activity), 50°C (>168 h 90% activity), and 55°C (half-life 48 h). Chitinase Chi1 has broad substrate specificity, and converts chitin, chitosan, modified chitosan and chitin oligosaccharides. The activity of chitinase Chi1 is strongly affected by the degree of deacetylation (DDA), molecular weight (Mw) and side chain modification of chitosan. Chitinase Chi1 releases mainly (GlcNAc)2 from insoluble chitin and chito-oligosaccharides with a polymerization degree (DP) ranging from 2 to 12 from chitosan, in a processive way. Chitinase Chi1 shows higher activity towards chitin oligosaccharides (GlcNAc)4-6 than towards (GlcNAc)3 and is inactive for (GlcNAc)2. During hydrolysis, oligosaccharides bind at subsites -2 to +2 in the enzyme’s active site. Chitinase Chi1 can be used for chitin valorisation and for production of chitin- and chito-oligosaccharides at industrial scale.Hide Abstract
Systems analysis of the family Glycoside Hydrolase family 18 enzymes from Cellvibrio japonicus characterizes essential chitin degradation functions.
Monge, E. C., Tuveng, T. R., Vaaje-Kolstad, G., Eijsink, V. G. & Gardner, J. G. (2018). Journal of Biological Chemistry, jbc-RA117.
Understanding the strategies used by bacteria to degrade polysaccharides constitutes an invaluable tool for biotechnological applications. Bacteria are major mediators of polysaccharide degradation in nature, however the complex mechanisms used to detect, degrade, and consume these substrates are not well understood, especially for recalcitrant polysaccharides such as chitin. It has been previously shown that the model bacterial saprophyte Cellvibrio japonicus is able to catabolize chitin, but little is known about the enzymatic machinery underlying this capability. Previous analyses of the C. japonicus genome and proteome indicated the presence of four family 18 Glycoside Hydrolase (GH18) enzymes, and studies of the proteome indicated that all are involved in chitin utilization. Using a combination of in vitro and in vivo approaches, we have studied the roles of these four chitinases in chitin bioconversion. Genetic analyses showed that only the chi18D gene product is essential for the degradation of chitin substrates. Biochemical characterization of the four enzymes showed functional differences and synergistic effects during chitin degradation, indicating non-redundant roles in the cell. Transcriptomic studies revealed complex regulation of the chitin degradation machinery of C. japonicus and confirmed the importance of CjChi18D and CjLPMO10A, a previously characterized chitin-active enzyme. With this systems biology approach, we deciphered the physiological relevance of the GH18 enzymes for chitin degradation in C. japonicus, and the combination of in vitro and in vivo approaches provided a comprehensive understanding of the initial stages of chitin degradation by this bacterium.Hide Abstract
An ancient family of lytic polysaccharide monooxygenases with roles in arthropod development and biomass digestion.
Sabbadin, F., Hemsworth, G. R., Ciano, L., Henrissat, B., Dupree, P., Tryfona, T., Marques, R. D. S., Sweeney, S. T., Besser, K., Elias, L., Pesante, G., Li, Y., Dowle, A. A., Bates, R., Gomez, L. D., Simister, R., Davies, G. J., Walton, P. H., Bruce, N. C. & Pesante, G. (2018). Nature communications, 9(1), 756.
Thermobia domestica belongs to an ancient group of insects and has a remarkable ability to digest crystalline cellulose without microbial assistance. By investigating the digestive proteome of Thermobia, we have identified over twenty members of an uncharacterized family of lytic polysaccharide monooxygenases (LPMOs). We show that this LPMO family spans across several clades of the Tree of Life, is of ancient origin and was recruited by early arthropods with possible roles in remodelling endogenous chitin scaffolds during development and metamorphosis. Based on our in-depth characterization of Thermobia’s LPMOs, we propose that diversification of these enzymes towards cellulose digestion might have endowed ancestral insects with an effective biochemical apparatus for biomass degradation, allowing the early colonization of land during the Paleozoic Era. The vital role of LPMOs in modern agricultural pests and disease vectors offers new opportunities to help tackle global challenges in food security and the control of infectious diseases.Hide Abstract
Krolicka, M., Hinz, S. W., Koetsier, M. J., Eggink, G., van den Broek, L. A. & Boeriu, C. G. (2018). Applied Microbiology and Biotechnology, 102(17), 7441-7454.
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.Hide Abstract
Characterization and synergistic action of a tetra‐modular lytic polysaccharide monooxygenase from Bacillus cereus.
Mutahir, Z., Mekasha, S., Loose, J. S., Abbas, F., Vaaje‐Kolstad, G., Eijsink, V. G. & Forsberg, Z. (2018). FEBS Letters, 592, 2562-2571.
Lytic polysaccharide monooxygenases (LPMOs) contribute to enzymatic conversion of recalcitrant polysaccharides such as chitin and cellulose and may also play a role in bacterial infections. Some LPMOs are multimodular, the implications of which remain only partly understood. We have studied the properties of a tetra‐modular LPMO from the food poisoning bacterium Bacillus cereus (named BcLPMO10A). We show that BcLPMO10A, comprising an LPMO domain, two fibronectin‐type III (FnIII)‐like domains, and a carbohydrate‐binding module (CBM5), is a powerful chitin‐active LPMO. While the role of the FnIII domains remains unclear, we show that enzyme functionality strongly depends on the CBM5, which, by promoting substrate binding, protects the enzyme from inactivation. BcLPMO10A enhances the activity of chitinases during the degradation of α-chitin.Hide Abstract
Berton, P., Shamshina, J. L., Ostadjoo, S., King, C. A. & Rogers, R. D. (2018). Carbohydrate Polymers, 199, 228-235.
Chitin, one of Nature’s most abundant biopolymers, can be obtained by either traditional chemical pulping or by extraction using the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate. The IL extraction and coagulation process provides access to a unique chitin, with an open hydrated gel-like structure. Here, enzymatic hydrolysis of this chitin hydrogel, dried shrimp shell, chitin extracted from shrimp shells using IL and then dried, and commercial chitin was carried out using chitinase from Streptomyces griseus. The enzymatic hydrolysis of shrimp shells resulted only in the monomer N-acetylglucosamine, while much higher amounts of the dimer (N, N′-diacetylchitobiose) compared to the monomer were detected when using all forms of ‘pure’ chitin. Interestingly, small amounts of the trimer (N, N′,N′′-triacetylchitotriose) were also detected when the IL-chitin hydrogel was used as substrate. Altogether, our findings indicate that the product distribution and yield are highly dependent on the substrate selected for the reaction and its hydrated state.Hide Abstract
Nareddy, P. K. & Swamy, M. J. (2017). International Journal of Biological Macromolecules, In Press.
In plants, chitooligosaccharide-binding phloem exudate lectins play an important role in the defense mechanism against parasites. Here, we investigated the thermal and chaotrope-induced unfolding of cucumber (Cucumis sativus) phloem exudate lectin (CPL). Circular dichroism (CD) spectroscopic studies indicate that the secondary and tertiary structures of CPL are essentially unaltered up to 90°C. Consistent with this, differential scanning calorimetric studies revealed that CPL is highly thermostable and undergoes a cooperative thermal unfolding transition centered at 97.6°C. The unfolding process was calorimetrically irreversible, and could be described by a non-two-state model, suggesting that upon undergoing a reversible unfolding transition the protein attains a final state in an irreversible step. The ratio of calorimetric and van’t Hoff enthalpies (ΔHc/ΔHv/) was >1.0, suggesting that the two monomers in the dimeric protein unfold at the same temperature. CD spectra recorded at different pH indicated that the secondary and tertiary structures of the protein are nearly unaltered in the pH range 3.0-10.0. Guanidine hydrochloride-induced unfolding studies indicate that chemical denaturation of CPL can also be described by a two-state process, without involving any intermediate. The stability of CPL to high temperatures and large variations of pH appear to be particularly suited for its role in plant defense.Hide Abstract
Moon, C., Seo, D. J., Song, Y. S., Hong, S. H., Choi, S. H. & Jung, W. J. (2017). Microbial Pathogenesis, 113, 218-224.
Serratia marcescens PRNK-1, which has strong chitinolytic activity, was isolated from cockroaches (Periplaneta Americana L.). The chitinase from S. marcescens PRNK-1 was characterized after incubation in a 0.5% colloidalchitin medium at 30°C for 3 days. The molecular weights of three bands after staining for chitinase activity were approximately 34, 41, and 48 kDa on an SDS-PAGE gel. S. marcescens PRNK-1 strain strongly inhibited hyphal growth of Rhizoctonia solani and Fusarium oxysporum. Thin-layer chromatography(TLC) and high performance liquid chromatograph (HPLC) analyses were conducted to investigate the degradation patterns of N-acetyl-chitooligosaccharides by PRNK-1 chitinase. The N-acetyl-chitooligosaccharides: N-acetyl-chitin dimer (GlcNAc)2, N-acetyl-chitin trimer (GlcNAc)3, and N-acetyl-chitin tetramer (GlcNAc)4 were degraded to (GlcNAc)1-3 on a TLC plate. In an additional experiment, (GlcNAc)6 was degraded to (GlcNAc)1-4 on a TLC plate. The optimal temperature for chitinase activity of the PRNK-1 was 50°C, producing 32.8 units/mL. As seen via TLC, the highest degradation of (GlcNAc)4 by PRNK-1 chitinase occurred with 50°C incubation. The optimal pH for chitinase activity of PRNK-1 was pH 5.5, producing 24.6 units/mL. As seen via TLC, the highest degradation of (GlcNAc)4 by PRNK-1 chitinase occurred at pH 5.0-6.0. These results indicate that chitinase produced from S. marcescens PRNK-1 strain showed strong antifungal activity and potential of production of N-acetyl-chitooligosaccharides.Hide Abstract
Regel, E. K., Weikert, T., Niehues, A., Moerschbacher, B. M. & Singh, R. (2017). Biotechnology and Bioengineering, In Press.
Partially acetylated chitosan oligosaccharides (paCOS) have various potential applications in agriculture, biomedicine and pharmaceutics due to their suitable bioactivities. One method to produce paCOS is partial chemical hydrolysis of chitosan polymers, but that leads to poorly defined mixtures of oligosaccharides. However, the effective production of defined paCOS is crucial for fundamental research and for developing applications. A more promising approach is enzymatic depolymerization of chitosan using chitinases or chitosanases, as the substrate specificity of the enzyme determines the composition of the oligomeric products. Protein-engineering of these enzymes to alter their substrate specificity can overcome the limitations associated with naturally occurring enzymes and expand the spectrum of specific paCOS that can be produced. Here, engineering the substrate specificity of Bacillus sp. MN chitosanase is described for the first time. Two muteins with active site substitutions can accept N-acetyl-D-glucosamine units at their subsite (-2), which is impossible for the wildtype enzyme.Hide Abstract