Kinetic characterization of Aspergillus niger chitinase CfcI using a HPAEC-PAD method for native chitin oligosaccharides

Separation, purification and structural characterization of marine oligosaccharides: A comprehensive and systematic review of chromatographic methods

Marine oligosaccharides have now been applied in a wide range of industry due to various kinds of physiological activities. However, the oligosaccharides with different polymeric degrees (Dps) differed in physiological activities and applicable fields. So it is promising and essential to separate, purify and structurally characterize these oligosaccharides for understanding their structure-function relationship. This review will summarize the lasted developments in the separation, purification and structural characterization of marine oligosaccharides, including the alginate oligosaccharides, carrageenan oligosaccharides, agar oligosaccharides, chitin oligosaccharides and chitosan oligosaccharides, emphasizing the successful examples of methods for separation and purification. Furthermore, an outlook for preparation of functional oligosaccharides in food biotechnology and agriculture fields is also included. This comprehensive review could definitely promote the utilization of marine functional polysaccharides for food and agriculture.

Plant root associated chitinases: structures and functions

Chitinases degrade chitin, a linear homopolymer of β-1,4-linked N-acetyl-D-glucosamine (GlcNAc) residues found in the cell walls of fungi and the exoskeletons of arthropods. They are secreted by the roots into the rhizosphere, a complex and dynamic environment where intense nutrient exchange occurs between plants and microbes. Here we modeled, expressed, purified, and characterized Zea mays and Oryza sativa root chitinases, and the chitinase of a symbiotic bacterium, Chitinophaga oryzae 1303 for their activities with chitin, di-, tri-, and tetra-saccharides and Aspergillus niger, with the goal of determining their role(s) in the rhizosphere and better understanding the molecular mechanisms underlying plant-microbe interactions. We show that Zea mays basic endochitinase (ZmChi19A) and Oryza sativa chitinase (OsChi19A) are from the GH19 chitinase family. The Chitinophaga oryzae 1303 chitinase (CspCh18A) belongs to the GH18 family. The three enzymes have similar apparent K M values of (20-40 µM) for the substrate 4-MU-GlcNAc3. They vary in their pH and temperature optima with OsChi19A activity optimal between pH 5-7 and 30-40°C while ZmChi19A and CspCh18A activities were optimal at pH 7-9 and 50-60°C. Modeling and site-directed mutation of ZmChi19A identified the catalytic cleft and the active residues E147 and E169 strategically positioned at ~8.6Å from each other in the folded protein. Cleavage of 4-MU-GlcNAc3 was unaffected by the absence of the CBD but diminished in the absence of the flexible C-terminal domain. However, unlike for the soluble substrate, the CBD and the newly identified flexible C-terminal domain were vital for inhibiting Aspergillus niger growth. The results are consistent with the involvement of the plant chitinases in defense against pathogens like fungi that have chitin exoskeletons. In summary, we have characterized the functional features and structural domains necessary for the activity of two plant root chitinases that are believed to be involved in plant defense and a bacterial chitinase that, along with the plant chitinases, may participate in nutrient recycling in the rhizosphere.

N-acetyl-d-glucosamine-based oligosaccharides from chitin: Enzymatic production, characterization and biological activities

Chitin, the second most abundant biopolymer, possesses diverse applications in the food, agricultural, and pharmaceutical industries due to its functional properties. However, the potential applications of chitin are limited owing to its high crystallinity and low solubility. N-acetyl chitooligosaccharides and lacto-N-triose II, the two types of GlcNAc-based oligosaccharides, can be obtained from chitin by enzymatic methods. With their lower molecular weights and improved solubility, these two types of GlcNAc-based oligosaccharides display more various beneficial health effects when compared to chitin. Among their abilities, they have exhibited antioxidant, anti-inflammatory, anti-tumor, antimicrobial, and plant elicitor activities as well as immunomodulatory and prebiotic effects, which suggests they have the potential to be utilized as food additives, functional daily supplements, drug precursors, elicitors for plants, and prebiotics. This review comprehensively covers the enzymatic methods used for the two types of GlcNAc-based oligosaccharides production from chitin by chitinolytic enzymes. Moreover, current advances in the structural characterization and biological activities of these two types of GlcNAc-based oligosaccharides are summarized in the review. We also highlight current problems in the production of these oligosaccharides and trends in their development, aiming to offer some directions for producing functional oligosaccharides from chitin.

Influence of a 4'-substituent on the efficiency of flavonol-based fluorescent indicators of β-glycosidase activity

This article presents novel fluorescent probes, based on the excited-state intramolecular proton transfer (ESIPT) phenomenon and flavonols, sensitive to the action of specific glycosidases. 4'-Substituted flavonols were synthesized, using various approaches, and glycosylated with d-glucose, N-acetyl-d-glucosamine and d-glucuronic acid. Evaluation of the β-glycosidase activities was performed in neutral and acidic pH. In all the cases examined, an acidic environment accelerated enzymatic hydrolysis. It was demonstrated that the 4'-chloroflavonyl glycosides of all sugars tested, both in neutral and acidic pH, are the ones most sensitive to the presence of hydrolase. In turn, 4'-dimethylaminoflavonyl glucoside is not sensitive to glucosidase action at all. Generally, the rate of enzymatic hydrolysis increases as the electron-withdrawing nature of the 4'-substituent increases. An exception is the trifluoromethyl group which, in spite of having the most favourable Hammett constant, does not contribute enough to increase the rate of hydrolysis of its glucoside. The presented experimental results are supported by the electrostatic potential (ESP) analysis and related to the mechanisms of glycoside bond enzymatic hydrolysis.

ChiE1 from Coprinopsis cinerea is Characterized as a Processive Exochitinase and Revealed to Have a Significant Synergistic Action with Endochitinase ChiIII on Chitin Degradation

Fruiting bodies that exhibit strong autolysis of Coprinopsis cinerea are a good resource for the chitinolytic system. In this study, a new Chitinase ChiE1 from C. cinerea was cloned, heterologously expressed, and characterized. Biochemical analysis demonstrated that ChiE1 is an exochitinase with a processive mode of action. Although ChiE1 contains only a single catalytic domain without a binding domain, it can bind to and degrade insoluble chitin powder and colloidal chitin. The combination of ChiE1 and C. cinerea endochitinase ChiIII could increase the amount of reducing sugar released from chitin powder by approximately 120% compared to using ChiE1 and ChiIII alone. The synergistic action of ChiE1 and ChiIII on degradation of chitin powder is higher than all previously reported synergism of chitinases. The recombinant Chitinase ChiE1 expressed in Pichia pastoris may be used as a synergistic chitinase for a reconstituted chitinolytic system for agricultural, biological, and environmental applications.

Quantitative Kinetic Characterization of Glycoside Hydrolases Using High-Performance Anion-Exchange Chromatography (HPAEC)

High-performance anion-exchange chromatography coupled to pulsed amperometric detection (HPAEC-PAD) is a powerful analytical technique enabling the high-resolution separation and sensitive quantification of oligosaccharides. Here, we describe a general method for the determination of glycoside hydrolase kinetics that harnesses the intrinsic power of HPAEC-PAD to simultaneously monitor the release of multiple products under conditions of low substrate conversion. Thus, the ability to track product release under initial-rate conditions with substrate concentrations as low as 5 μM enables the determination of Michaelis-Menten kinetics for glycosidase activities, including hydrolysis and transglycosylation. This technique may also be readily extended to other carbohydrate-active enzymes (CAZymes), including polysaccharide lyases, and glycosyl transferases.

Validated HPAEC-PAD Method for the Determination of Fully Deacetylated Chitooligosaccharides

An efficient and sensitive analytical method based on high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was established for the simultaneous separation and determination of glucosamine (GlcN)₁ and chitooligosaccharides (COS) ranging from (GlcN)₂ to (GlcN)₆ without prior derivatization. Detection limits were 0.003 to 0.016 mg/L (corresponding to 0.4-0.6 pmol), and the linear range was 0.2 to 10 mg/L. The optimized analysis was carried out on a CarboPac-PA100 analytical column (4 × 250 mm) using isocratic elution with 0.2 M aqueous sodium hydroxide-water mixture (10:90, v/v) as the mobile phase at a 0.4 mL/min flow rate. Regression equations revealed a good linear relationship (R² = 0.9979-0.9995, n = 7) within the test ranges. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated HPAEC-PAD method was readily applied for the quantification of (GlcN)_1-6 in a commercial COS technical concentrate. The established method was also used to monitor the acid hydrolysis of a COS technical concentrate to ensure optimization of reaction conditions and minimization of (GlcN)₁ degradation.

The Modes of Action of ChiIII, a Chitinase from Mushroom Coprinopsis cinerea, Shift with Changes in the Length of GlcNAc Oligomers

A putative class III endochitinase (ChiIII) was reported previously to be expressed dominantly in fruiting bodies of Coprinopsis cinerea, and its expression levels increased with the maturation of the fruiting bodies. This paper further reports that ChiIII is a novel chitinase with exo- and endoactivities. When the substrate was (GlcNAc)3-5, ChiIII exhibited exoactivity, releasing GlcNAc processively from the reducing end of (GlcNAc)3-5; when the substrate was (GlcNAc)6-7, the activity of ChiIII shifted to an endoacting enzyme, randomly splitting chitin oligosaccharides to various shorter oligosaccharides. This shift in the mode of action of ChiIII may be related to its stronger hydrolytic capacity to degrade chitin in fungal cell walls. The predicted structure of ChiIII shows that it lacks the α+β domain insertion; however, its substrate binding cleft seems to be deeper than that of common endochitinases but shallower and more open than that of common exochitinases, which may be related to its exo- and endohydrolytic activities.

A novel analytical method for d-glucosamine quantification and its application in the analysis of chitosan degradation by a minimal enzyme cocktail

Enzymatic depolymerization of chitosan, a β-(1,4)-linked polycationic polysaccharide composed of d-glucosamine (GlcN) and N-acetyl-d-glucosamine (GlcNAc) provides a possible route to the exploitation of chitin-rich biomass. Complete conversion of chitosan to mono-sugars requires the synergistic action of endo- and exo- chitosanases. In the present study we have developed an efficient and cost-effective chitosan-degrading enzyme cocktail containing only two enzymes, an endo-attacking bacterial chitosanase, ScCsn46A, from Streptomyces coelicolor, and an exo-attacking glucosamine specific β-glucosaminidase, Tk-Glm, from the archaeon Thermococcus kodakarensis KOD1. Moreover, we developed a fast, reliable quantitative method for analysis of GlcN using high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The sensitivity of this method is high and less than 50 pmol was easily detected, which is about 1000-fold better than the sensitivity of more commonly used detection methods based on refractive index. We also obtained qualitative insight into product development during the enzymatic degradation reaction by means of ElectroSpray Ionization-Mass Spectrometry (ESI-MS).