Chondroitin Lyase from a Marine Arthrobacter sp. MAT3885 for the Production of Chondroitin Sulfate Disaccharides

The structures and applications of microbial chondroitin AC lyase

As an important glycosaminoglycan hydrolase, chondroitin lyases can hydrolyze chondroitin sulfate (CS) and release disaccharides and oligosaccharides. They are further divided into chondroitin AC, ABC, and B lyases according to their spatial structure and substrate specificity. Chondroitin AC lyase can hydrolyze chondroitin sulfate A (CS-A), chondroitin sulfate C (CS-C), and hyaluronic acid (HA), making it an essential biocatalyst for the preparation of low molecular weight chondroitin sulfate, analysis of the structure of the chondroitin sulfate, treatment of spinal cord injury, and purification of heparin. This paper provides an overview of reported chondroitin AC lyases, including their properties and the challenges faced in industrial applications. Up to now, although many attempts have been adopted to improve the enzyme properties, the most important factors are still the low activity and stability. The relations between the stability of the enzyme and the spatial structure were also summarized and discussed. Also perspectives for remodeling the enzymes with protein engineering are included.

Characterization of a Thermostable and Surfactant-Tolerant Chondroitinase B from a Marine Bacterium Microbulbifer sp. ALW1

Chondroitinase plays an important role in structural and functional studies of chondroitin sulfate (CS). In this study, a new member of chondroitinase B of PL6 family, namely ChSase B6, was cloned from marine bacterium Microbulbifer sp. ALW1 and subjected to enzymatic and structural characterization. The recombinant ChSase B6 showed optimum activity at 40 °C and pH 8.0, with enzyme kinetic parameters of Km and Vmax against chondroitin sulfate B (CSB) to be 7.85 µg/mL and 1.21 U/mg, respectively. ChSase B6 demonstrated thermostability under 60 °C for 2 h with about 50% residual activity and good pH stability under 4.0-10.0 for 1 h with above 60% residual activity. In addition, ChSase B6 displayed excellent stability against the surfactants including Tween-20, Tween-80, Trion X-100, and CTAB. The degradation products of ChSase B6-treated CSB exhibited improved antioxidant ability as a hydroxyl radical scavenger. Structural analysis and site-directed mutagenesis suggested that the conserved residues Lys248 and Arg269 were important for the activity of ChSase B6. Characterization, structure, and molecular dynamics simulation of ChSase B6 provided a guide for further tailoring for its industrial application for chondroitin sulfate bioresource development.

A novel chondroitin AC lyase from Pedobacter xixiisoli: Cloning, expression, characterization and the application in the preparation of oligosaccharides

Chondroitin AC lyase can efficiently hydrolyze chondroitin sulfate (CS) to low molecule weight chondroitin sulfate, which has been widely used in clinical therapy, including anti-tumor, anti-oxidation, hypolipidemic, and anti-inflammatory. In this work, a novel chondroitin AC lyase from Pedobacter xixiisoli (PxchonAC) was cloned and overexpressed in Escherichia coli BL21 (DE3). The characterization of PxchonAC showed that it has specific activities on chondroitin sulfate A, Chondroitin sulfate C and hyaluronic acid with 428.77, 270.57, and 136.06 U mg^-1, respectively. The K_m and V_max of PxchonAC were 0.61 mg mL^-1 and 670.18 U mg^-1 using chondroitin sulfate A as the substrate. The enzyme had a half-life of roughly 660 min at 37 °C in the presence of Ca²⁺ and remained a residual activity of 54 % after incubated at 4 °C for 25 days. Molecular docking revealed that Asn123, His223, Tyr232, Arg286, Arg290, Asn372, and Glu374 were mainly involved in the substrate binding. The enzymatic hydrolysis product was analyzed by gel permeation chromatography, demonstrating PxchonAC could hydrolyze CS efficiently.

Research and Application of Chondroitin Sulfate/Dermatan Sulfate-Degrading Enzymes

Chondroitin sulfate (CS) and dermatan sulfate (DS) are widely distributed on the cell surface and in the extracellular matrix in the form of proteoglycan, where they participate in various biological processes. The diverse functions of CS/DS can be mainly attributed to their high structural variability. However, their structural complexity creates a big challenge for structural and functional studies of CS/DS. CS/DS-degrading enzymes with different specific activities are irreplaceable tools that could be used to solve this problem. Depending on the site of action, CS/DS-degrading enzymes can be classified as glycosidic bond-cleaving enzymes and sulfatases from animals and microorganisms. As discussed in this review, a few of the identified enzymes, particularly those from bacteria, have wildly applied to the basic studies and applications of CS/DS, such as disaccharide composition analysis, the preparation of bioactive oligosaccharides, oligosaccharide sequencing, and potential medical application, but these do not fulfill all of the needs in terms of the structural complexity of CS/DS.

Synthesis of structurally defined chondroitin sulfate: Paving the way to the structure-activity relationship studies

Chondroitin sulfate (CS) is one of the major and widespread glycosaminoglycans, a family of structurally complex, linear, anionic hetero-co-polysaccharides. CS plays a vital role in various normal physiological and pathological processes, thus, showing varieties of biological activities, such as anti-oxidation, anti-atherosclerosis, anti-thrombosis, and insignificant immunogenicity. However, the heterogeneity of the naturally occurring CS potentially leads to function unspecific and limits further structure-activity relationship studies. Therefore, the synthesis of CS with well-defined and uniform chain lengths is of major interest for the development of reliable drugs. In this review, we examine the remarkable progress that has been made in the chemical, enzymatic and chemoenzymatic synthesis of CS and its derivatives, providing a broad spectrum of options to access CS of well controlled chain lengths.

Cloning, Expression, and Characterization of a New Glycosaminoglycan Lyase from Microbacterium sp. H14

Glycosaminoglycan (GAG) lyase is an effective tool for the structural and functional studies of glycosaminoglycans and preparation of functional oligosaccharides. A new GAG lyase from Microbacterium sp. H14 was cloned, expressed, purified, and characterized, with a molecular weight of approximately 85.9 kDa. The deduced lyase HCLaseM belonged to the polysaccharide lyase (PL) family 8. Based on the phylogenetic tree, HCLaseM could not be classified into the existing three subfamilies of this family. HCLaseM showed almost the same enzyme activity towards hyaluronan (HA), chondroitin sulfate A (CS-A), CS-B, CS-C, and CS-D, which was different from reported GAG lyases. HCLaseM exhibited the highest activities to both HA and CS-A at its optimal temperature (35 °C) and pH (pH 7.0). HCLaseM was stable in the range of pH 5.0–8.0 and temperature below 30 °C. The enzyme activity was independent of divalent metal ions and was not obviously affected by most metal ions. HCLaseM is an endo-type enzyme yielding unsaturated disaccharides as the end products. The facilitated diffusion effect of HCLaseM is dose-dependent in animal experiments. These properties make it a candidate for further basic research and application.

Cloning and Characterization of a Chondroitin AC Exolyase from Arthrobacter sp. SD-04

Glycosaminoglycans (GAGs) and their low-molecular weight derivates have received considerable interest in terms of their potential clinical applications, and display a wide variety of pharmacological and pharmacokinetic properties. Structurally distinct GAG chains can be prepared by enzymatic depolymerization. A variety of bacterial chondroitin sulfate (CS) lyases have been identified, and have been widely used as catalysts in this process. Here, we identified a putative chondroitin AC exolyase gene, AschnAC, from an Arthrobacter sp. strain found in a CS manufacturing workshop. We expressed the enzyme, AsChnAC, recombinantly in Escherichia coli, then purified and characterized it in vitro. The enzyme indeed displayed exolytic cleavage activity toward HA and various CSs. Removing the putative N-terminal secretion signal peptide of AsChnAC improved its expression level in E. coli while maintaining chondroitin AC exolyase activity. This novel catalyst exhibited its optimal activity in the absence of added metal ions. AsChnAC has potential applications in preparation of low-molecular weight GAGs, making it an attractive catalyst for further investigation.

Modification of linear (β1→3)-linked gluco-oligosaccharides with a novel recombinant β-glucosyltransferase (trans-β-glucosidase) enzyme from Bradyrhizobium diazoefficiens

Recently, we have shown that glycoside hydrolases enzymes of family GH17 from proteobacteria (genera Pseudomonas, Azotobacter) catalyze elongation transfer reactions with laminari-oligosaccharides generating (β1→3) linkages preferably and to a lesser extent (β1→6) or (β1→4) linkages. In the present study, the cloning and characterization of the gene encoding the structurally very similar GH17 domain of the NdvB enzyme from Bradyrhizobium diazoefficiens, designated Glt20, as well as its catalytic properties are described. The Glt20 enzyme was strikingly different from the previously investigated bacterial GH17 enzymes, both regarding substrate specificity and product formation. The Azotobacter and Pseudomonas enzymes cleaved the donor laminari-oligosaccharide substrates three or four moieties from the non-reducing end, generating linear oligosaccharides. In contrast, the Glt20 enzyme cleaved donor laminari-oligosaccharide substrates two glucose moieties from the reducing end, releasing laminaribiose and transferring the remainder to laminari-oligosaccharide acceptor substrates creating only (β1→3)(β1→6) branching points. This enables Glt20 to transfer larger oligosaccharide chains than the other type of bacterial enzymes previously described, and helps explain the biologically significant formation of cyclic β-glucans in B. diazoefficiens.

Uncovering the Catalytic Direction of Chondroitin AC Exolyase: FROM THE REDUCING END TOWARDS THE NON-REDUCING END

Glycosaminoglycans (GAGs) are polysaccharides that play vital functional roles in numerous biological processes, and compounds belonging to this class have been implicated in a wide variety of diseases. Chondroitin AC lyase (ChnAC) (EC 4.2.2.5) catalyzes the degradation of various GAGs, including chondroitin sulfate and hyaluronic acid, to give the corresponding disaccharides containing an Δ(4)-unsaturated uronic acid at their non-reducing terminus. ChnAC has been isolated from various bacteria and utilized as an enzymatic tool for study and evaluating the sequencing of GAGs. Despite its substrate specificity and the fact that its crystal structure has been determined to a high resolution, the direction in which ChnAC catalyzes the cleavage of oligosaccharides remain unclear. Herein, we have determined the structural cues of substrate depolymerization and the cleavage direction of ChnAC using model substrates and recombinant ChnAC protein. Several structurally defined oligosaccharides were synthesized using a chemoenzymatic approach and subsequently cleaved using ChnAC. The degradation products resulting from this process were determined by mass spectrometry. The results revealed that ChnAC cleaved the β1,4-glycosidic linkages between glucuronic acid and glucosamine units when these bonds were located on the reducing end of the oligosaccharide. In contrast, the presence of a GlcNAc-α-1,4-GlcA unit at the reducing end of the oligosaccharide prevented ChnAC from cleaving the GalNAc-β1,4-GlcA moiety located in the middle or at the non-reducing end of the chain. These interesting results therefore provide direct proof that ChnAC cleaves oligosaccharide substrates from their reducing end toward their non-reducing end. This conclusion will therefore enhance our collective understanding of the mode of action of ChnAC.