Chondroitin AC Lyase Research Articles

Introducing Ion Mobility Mass Spectrometry in Brain Glycosaminoglycomics: Application to Chondroitin/Dermatan Sulfate Octasaccharide Domains.

Glycosaminoglycans (GAGs) are sulfated linear O-glycan chains abundantly expressed in the extracellular matrix (ECM). Among GAGs, chondroitin sulfate (CS) and dermatan sulfate (DS) play important roles at the brain level, where the distribution and location of the sulfates within the CS/DS chains are responsible for numerous biological events. The diversity of the neural hybrid CS/DS expressed in the brain and the need to elucidate their structure gave rise to considerable efforts toward the development of analytical methods able to discover novel regularly and irregularly sulfated domains. In this context, we report here the introduction of ion mobility separation (IMS) mass spectrometry (MS) in brain glycosaminoglycomics. Based on IMS MS and tandem MS (MS/MS) by collision-induced dissociation (CID), we have developed a powerful approach for the screening and structural analysis of neural CS/DS and optimized and validated the method for the structural analysis of octasaccharides that were released from brain proteoglycans by β-elimination and pooled after chain depolymerization using chondroitin AC lyase. The IMS MS data revealed the separation of CS/DS octamers into mobility families based on the amount of sulfation. Among the discovered oversulfated domains, of major biological importance is the pentasulfated-[4,5-Δ-GlcAGalNAc(IdoAGalNAc)3], for which the (-) nanoESI IMS CID MS/MS analysis disclosed through the presence of distinct drift times, the incidence of two isomers. Moreover, the generated fragment ions revealed an uncommon trisulfated motif and an uncommon pentasulfated motif. Hence, using IMS MS and CID MS/MS, novel brain-related CS/DS domains of atypical sulfation patterns were discovered and structurally characterized in detail.

Characterization and Structural Analysis of a Novel Carbohydrate-Binding Module from Family 96 with Chondroitin Sulfate-Specific Binding Capacity.

Chondroitin sulfate (CS) is the predominant glycosaminoglycan within the human body and is widely applied in various industries. Carbohydrate-binding modules (CBMs) possessing the capacity for carbohydrate recognition are verified to be important tools for polysaccharide investigation. Only one CS-specific CBM, PhCBM100, has hitherto been characterized. In the present study, two CBM96 domains present in the same putative PL8_3 chondroitin AC lyase were discovered and recombinantly expressed. The results of microtiter plate assays and affinity gel electrophoresis assays showed that the two corresponding proteins, DmCBM96-1 and DmCBM96-2, bind specifically to CSs. The crystal structure of DmCBM96-1 was determined at a 2.20 Å resolution. It adopts a β-sandwich fold comprising two antiparallel β-sheets, showing structural similarities to TM6-N4, which is the founding member of the CBM96 family. Site mutagenesis analysis revealed that the residues of Arg27, Lys45, Tyr51, Arg53, and Arg157 are critical for CS binding. The characterization of the two CBM96 proteins demonstrates the diverse ligand specificity of the CBM96 family and provides promising tools for CS investigation.

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.

A Novel Chondroitin AC Lyase With Broad Substrate Specificity From Pedobacter rhizosphaerae: Cloning, Expression, and Characterization.

Chondroitin AC lyase (ChSaseAC) is one of the essential polysaccharides lyases in low molecular chondroitin sulfate production. In this work, a novel PrChSaseAC from Pedobacter rhizosphaerae was successfully cloned, expressed in Escherichia coli. After optimizing the induction, the recombinant PrChSaseAC could be expressed efficiently at 0.1 mM IPTG, 25°C, and 12 h induction. Then, it was purified with Ni-NTA affinity chromatography. The characterization of the purified PrChSaseAC showed that it had high specific activity and good storage stability, which would favor the production of low molecular weight chondroitin sulfate. It also displayed activity toward chondroitin sulfate C and hyaluronic acid. PrChSaseAC had the highest activity at pH 7.5, 37°C, 10 mM Ca2+, and 5 mg/ml of chondroitin sulfate A. Molecular docking of substrate and enzyme showed the interactions between the enzyme and substrate; it revealed that the enzyme showed high activity to CS-A and hyaluronic acid, but lower activity to CS-C attributed to the structure of the binding pocket. The high stability and specific activity of the enzyme will benefit the industrial production or clinical treatment.

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 Km and Vmax 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.

Validation of a quantitative PCR assay for the detection of 2 Flavobacterium columnare genomovars.

Flavobacterium columnare is the causative agent of columnaris disease in a variety of fish hosts. Using modifications to previously established protocols, a quantitative PCR (qPCR) assay was validated for the detection of 2 predominant F. columnare genomovars. The oligonucleotide primer and probe combination was designed to amplify a 203-bp region of the chondroitin AC lyase gene (GenBank AY912281) of F. columnare. There were no significant differences in amplification between genomovars. Comparable quantities of genomic DNA from 10 F. columnare strains, 5 representatives of each genomovar, produced similar results. Serial dilutions of purified PCR product demonstrated the limit of sensitivity for the assay was ~ 10 copies per reaction. The presence of gill and spleen tissue did not significantly affect the sensitivity of the assay. Comparably, bacterial DNA detected from the liver and kidney was less sensitive than pure bacterial DNA. However, detection from these tissues was within one order of magnitude of other tissues, indicating this reduction may have minimal analytic significance. This validated assay was used to approximate the minimum infectious dose for F. columnare isolate 94-081 in channel catfish and assess bacterial loads in gill and kidney tissues 48 h post-infection.

Development of a species-specific polymerase chain reaction for highly sensitive detection of Flavobacterium columnare targeting chondroitin AC lyase gene

Columnaris disease, caused by Flavobacterium columnare, is an acute infection of gills and fins, that exists worldwide and causes remarkable losses in freshwater fish. The 16S rRNA gene is not a good candidate for primer design, since this gene has high identity among species in the same genus. In the present study, we developed a species-specific PCR for detection of Flavobacterium columnare based on the chondroitin AC lyase (cslA) gene. The cslA gene sequence from 13 F. columnare strains were aligned to design a specific primer set, Fcol-F and Fcol-R, based on conserved region of the gene. The new primer set produced a specific amplicon of 287 bp from 83 isolates of F. columnare but not from related or other bacterial pathogens. The PCR was sensitive and detected up to 3 pg of genomic DNA and as few as 7 colony-forming units of bacteria. The sensitivity was decreased tenfold when F. columnare gDNA was spiked into tissue samples. The designed primers precisely amplified F. columnare from skin and gills of infected fish, but not in those of clinically healthy fish, reflecting their possible use for diagnostic purposes.

Proteomic enzyme analysis of the marine fungus Paradendryphiella salina reveals alginate lyase as a minimal adaptation strategy for brown algae degradation

We set out to investigate the genetic adaptations of the marine fungus Paradendryphiella salina CBS112865 for degradation of brown macroalgae. We performed whole genome and transcriptome sequencing and shotgun proteomic analysis of the secretome of P. salina grown on three species of brown algae and under carbon limitation. Genome comparison with closely related terrestrial fungi revealed that P. salina had a similar but reduced CAZyme profile relative to the terrestrial fungi except for the presence of three putative alginate lyases from Polysaccharide Lyase (PL) family 7 and a putative PL8 with similarity to ascomycete chondroitin AC lyases. Phylogenetic and homology analyses place the PL7 sequences amongst mannuronic acid specific PL7 proteins from marine bacteria. Recombinant expression, purification and characterization of one of the PL7 genes confirmed the specificity. Proteomic analysis of the P. salina secretome when growing on brown algae, revealed the PL7 and PL8 enzymes abundantly secreted together with enzymes necessary for degradation of laminarin, cellulose, lipids and peptides. Our findings indicate that the basic CAZyme repertoire of saprobic and plant pathogenic ascomycetes, with the addition of PL7 alginate lyases, provide P. salina with sufficient enzymatic capabilities to degrade several types of brown algae polysaccharides.

Prebiotic Chondroitin Sulfate Disaccharide Isolated from Chicken Keel Bone Exhibiting Anticancer Potential Against Human Colon Cancer Cells

Chondroitin sulfate (CS)-Keel disaccharide (CSD) was produced by chondroitin AC lyase (PsPL8A) degradation of food grade CS-Keel polysaccharide isolated from chicken keel cartilage. PsPL8A showed specific activity, 340 ± 5.2 U mg−1 with CS-Keel polysaccharide. TLC showed CSD as the major product. CSD was purified by gel filtration and MS/MS, confirms it as C4S disaccharide. Structural characterization by FTIR and NMR showed presence of N-acetylgalactosamine and glucuronic acid. CSD displayed resistance to gastric juice with 23.7% hydrolysis at pH 1.0. CSD showed prebiotic score of 0.57 for L. acidophilus and 0.58 for B. infantis and produce SCFA products. MTT and morphological analysis confirmed, CSD (0.5 mg mL−1) does not decrease viability of mouse fibroblast (L929), but showed anti-proliferative potential against human colon cancer (HT-29) cell lines (80% inhibition). CSD treated HT-29 cells exhibit nuclear fragmentation and apoptosis. Prebiotic and anticancer potential of CSD can be utilized for functional food preparation and prevention of gastrointestinal disorders.

Antitumor effect of chondroitin AC lyase (PsPL8A) from Pedobacter saltans on melanoma and fibrosarcoma cell lines by in vitro analysis.

PGs are involved in cellular communication and cancer biology. The role of CS in melanoma and fibrosarcoma cell lines was explored by using chondroitin AC lyase (PsPL8A). The proliferation of mouse fibroblast L929, human melanoma (SK-Mel 28) and fibrosarcoma (HT-1080) cell lines after treatment with chondroitin AC lyase (PsPL8A) was studied by MTT assay. The mode of cell death was studied by Annexin-V FITC using flow cytometry and fluorescence microscopy. The alteration in mitochondrial cell potential was studied by JC-1 dye using fluorescence microscopy and flow cytometry. Treatment of L929 cells with PsPL8A imparts no cytotoxicity and showed no alteration in proliferation with nearly 95-98% cell viability. An overall 58% and 59% inhibition of SK-Mel 28 and HT-1080 cell proliferation was observed with 1.3 μM of PsPL8A after 24 h of incubation. The PsPL8A (1.3 μM) treated SK-Mel 28 and HT-1080 cells showed significant green fluorescence with annexin-V FITC under fluorescence microscopy and 56.6% and 35.5% apoptosis, respectively by flow cytometry analysis. The results of fluorescence microscopy and flow cytometry of SK-Mel 28 and HT-1080 upon treatment with PsPL8A (1.3 μM) for 24 h, gave green fluorescence due to dissipation of mitochondrial potential with JC-1 dye. Chondroitin AC lyase (PsPL8A) displayed anti-tumor potential against human melanoma SK-Mel 28 and fibrosarcoma HT-1080 cell lines, while the mouse fibroblast L929 cells were unaffected.

Insights into the structural characteristics and substrate binding analysis of chondroitin AC lyase (PsPL8A) from Pedobacter saltans

The structure of chondroitin AC lyase (PsPL8A) of family 8 polysaccharide lyase was characterized. Modeled PsPL8A structure showed, it contains N-terminal (α/α)6 incomplete toroidal fold and a layered β sandwich structure at C-terminal. Ramchandran plot displayed 98.5% residues in favoured and 1.2% in generously allowed region. Secondary structure of PsPL8A by CD revealed 27.31% α helices 22.7% β sheets and 49.9% random coils. Protein melting study showed, PsPL8A completely unfolds at 60°C. SAXS analysis showed, PsPL8A is fully folded in solution form. The ab initio derived dummy model of PsPL8A superposed well with its modeled structure excluding some α-helices and loop region. Structural superposition and docking analysis showed, N153, W105, H203, Y208, Y212, R266 and E349 were involved in catalysis. Mutants N153A, H203A, Y212F, R266A and E349A created by SDM revealed no residual activity. Isothermal titration calorimetry analysis of Y212F and H203A with C4S polysaccharide, showed moderate binding by Y212F (Ka=9.56±3.81×105) and no binding with H203A, showing active contribution of Y212 in substrate binding. Residues Y212 and H203 or R266 might act as general base and general acid respectively. Residues N153 and E349 are likely contributing in charge neutralization and stabilizing enolate anion intermediate during β-elimination.

The Complete Genome Sequence of the Fish Pathogen Tenacibaculum maritimum Provides Insights into Virulence Mechanisms.

Tenacibaculum maritimum is a devastating bacterial pathogen of wild and farmed marine fish with a broad host range and a worldwide distribution. We report here the complete genome sequence of the T. maritimum type strain NCIMB 2154T. The genome consists of a 3,435,971-base pair circular chromosome with 2,866 predicted protein-coding genes. Genes encoding the biosynthesis of exopolysaccharides, the type IX secretion system, iron uptake systems, adhesins, hemolysins, proteases, and glycoside hydrolases were identified. They are likely involved in the virulence process including immune escape, invasion, colonization, destruction of host tissues, and nutrient scavenging. Among the predicted virulence factors, type IX secretion-mediated and cell-surface exposed proteins were identified including an atypical sialidase, a sphingomyelinase and a chondroitin AC lyase which activities were demonstrated in vitro.

A new member of family 8 polysaccharide lyase chondroitin AC lyase (PsPL8A) from Pedobacter saltans displays endo- and exo-lytic catalysis

Chondroitin lyases are therapeutically important enzymes. The functional aspects of a chondroitin AC lyase (PsPL8A) from Pedobacter saltans DSM12145 were investigated. PsPL8A was cloned in to pET28a(+) vector, expressed in E. coli BL-21(DE3) cells exhibited a molecular size of approximately, 77kDa. PsPL8A displayed maximum activity with chondroitin 4-sulphate, C4S (489Umg−1) followed by chondroitin 6-sulphate, C6S (214Umg−1) and hyaluronic acid (43.2Umg−1). PsPL8A was maximally active at 39°C and pH 7.2. 100mM Na+ and 20mM Ca2+ ions enhanced the activity of PsPL8A by 2-fold. The time dependent TLC analysis of PsPL8A degraded products of C4S revealed the presence of higher degree of polymerization (DP) chondroitin sulphate (CS) oligosaccharides at initial stage, but after 1h, only ΔC4S disaccharide was produced as the major product. This result displayed that PsPL8A follows initially a concomitant endo- and exo-lytic mode which finally shifted to exolytic mode of catalysis. The oligosaccharides released were identified as di-, hexa-, octa- and dodeca-saccharide by ESI–MS analysis. The ΔC4S disaccharide showed a peak at m/z 458 (ESI–MS) while in MS/MS mode it gave the peak at m/z 300. ESI–MS/MS, 1H- and 13C- NMR analyses confirmed the structure of ΔC4S disaccharide product obtained after 24h reaction of C4S with PsPL8A. The enzyme reported in present study can be used for cancer mitigation, spinal cord injury treatment and CS oligosaccharides production which act as anti-inflammatory agents. This is the first study reporting the cloning and expression of chondroitin AC lyase from Pedobacter saltans DSM 12145.

Immunogenicity and protective role of antigenic regions from five outer membrane proteins of Flavobacterium columnare in grass carp Ctenopharyngodon idella

Flavobacterium columnare causes columnaris disease in freshwater fish. In the present study, the antigenic regions of five outer membrane proteins (OMPs), including zinc metalloprotease, prolyl oligopeptidase, thermolysin, collagenase and chondroitin AC lyase, were bioinformatically analyzed, fused together, and then expressed as a recombinant fusion protein in Escherichia coli. The expressed protein of 95.6 kDa, as estimated by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was consistent with the molecular weight deduced from the amino acid sequence. The purified recombinant protein was used to vaccinate the grass carp, Ctenopharyngodon idella. Following vaccination of the fish their IgM antibody levels were examined, as was the expression of IgM, IgD and IgZ immunoglobulin genes and other genes such as MHC Iα and MHC IIβ, which are also involved in adaptive immunity. Interleukin genes (IL), including IL-1β, IL-8 and IL-10, and type I and type II interferon (IFN) genes were also examined. At 3 and 4 weeks post-vaccination (wpv), significant increases in IgM antibody levels were observed in the fish vaccinated with the recombinant fusion protein, and an increase in the expression levels of IgM, IgD and IgZ genes was also detected following the vaccinations, thus indicating that an adaptive immune response was induced by the vaccinations. Early increases in the expression levels of IL and IFN genes were also observed in the vaccinated fish. At four wpv, the fish were challenged with F. columnare, and the vaccinated fish showed a good level of protection against this pathogen, with 39% relative percent survival (RPS) compared with the control group. It can be concluded, therefore, that the five OMPs, in the form of a recombinant fusion protein vaccine, induced an immune response in fish and protection against F. columnare.

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.

Identification of an unusually sulfated tetrasaccharide chondroitin/dermatan motif in mouse brain by combining chip‐nanoelectrospray multistage MS2‐MS4 and high resolution MS

Chondroitin sulfate (CS)/dermatan sulfate (DS) are often found in nature as hybrid glycosaminoglycan chains in various proteoglycans. In the recent years, several MS methods were developed for the determination of over-, regular-, and undersulfated CS/DS chains. In the present work, the released hybrid CS/DS isolated and purified from mouse brain were digested with chondroitin AC lyase. The depolymerized chains were separated by gel filtration chromatography. Collected tetrasaccharides were analyzed by fully automated (NanoMate robot) chip-based nanoESI high capacity ion trap multistage MS (MS(2) -MS(4) ) recently introduced in glycosaminoglycan research by our laboratory. The obtained data were confirmed by high resolution MS screening and MS/MS performed on QTOF instrument. NanoMate-high capacity ion trap MS and QTOF MS screening revealed the presence in the mixture of oversulfated tetrasaccharides bearing three and four sulfate groups as well as traces of regularly and undersulfated hexamers. Additionally, several saturated species as either tetramers or hexamers exhibiting different sulfate content were discovered in the analyzed fraction. This diversity of the sulfation status indicates that the mouse brain might contain several types of proteoglycans. The molecular ions corresponding to trisulfated-[4,5Δ-GlcA-GalNAc-IdoA-GalNAc] were subjected to multistage fragmentation by CID. Sequence analysis data allowed for the postulation of two rare structural motifs: [4,5Δ-GlcA-GalNAc(4S)-IdoA(2S,3S)-GalNAc] and [4,5Δ-GlcA-GalNAc-IdoA(2S,3S)-GalNAc(4S)], previously not reported in neural tissue.

Virulent and nonvirulent Flavobacterium columnare colony morphologies: characterization of chondroitin AC lyase activity and adhesion to polystyrene

Colony morphology variants of fish pathogenic Flavobacterium columnare were studied to clarify the role of colony morphology change in the virulence of the bacterium. Typical rhizoid colony (Rz) variants are virulent and moderately adherent, nonrhizoid rough (R) colony variants are nonvirulent and highly adherent, and soft colony (S) variants are nonvirulent and poorly adherent. Chondroitin AC lyase activity, adhesion to polystyrene at different temperatures and after modification of bacterial surface, and lipopolysaccharide (LPS) profiles of the variants were studied. The chondroitinase activity was significantly higher in the virulent, rhizoid variants than in the rough variants of the same strain. Temperature significantly increased the adhesion of rhizoid variants up to 20°C. Modification of bacterial surface suggested that adhesion molecules contain both carbohydrates and proteins. LPS did not differ between the variants of the same strain. The results suggest that in Fl. columnare both rhizoid colony morphology and high chondroitinase activity are needed for virulence and that temperature may promote the adhesion of the virulent variants to surfaces at fish farms. New information is produced on the virulence mechanisms of Fl. columnare and the reasons behind the survival of the bacterium at fish farms.

The K5 Lyase KflA Combines a Viral Tail Spike Structure with a Bacterial Polysaccharide Lyase Mechanism

K5 lyase A (KflA) is a tail spike protein (TSP) encoded by a K5A coliphage, which cleaves K5 capsular polysaccharide, a glycosaminoglycan with the repeat unit [-4)-betaGlcA-(1,4)- alphaGlcNAc(1-], displayed on the surface of Escherichia coli K5 strains. The crystal structure of KflA reveals a trimeric arrangement, with each monomer containing a right-handed, single-stranded parallel beta-helix domain. Stable trimer formation by the intertwining of strands in the C-terminal domain, followed by proteolytic maturation, is likely to be catalyzed by an autochaperone as described for K1F endosialidase. The structure of KflA represents the first bacteriophage tail spike protein combining polysaccharide lyase activity with a single-stranded parallel beta-helix fold. We propose a catalytic site and mechanism representing convergence with the syn-beta-elimination site of heparinase II from Pedobacter heparinus.

Structural characterization and antithrombin activity of dermatan sulfate purified from marine clam Scapharca inaequivalvis

Glycosaminoglycans from the body of marine clam Scapharca inaequivalvis were extracted at about 0.15- 0.18 mg/g of dry tissue, composed of dermatan sulfate (DS) (approx. 74%) and heparan sulfate (26%). After treatment with nitrous acid, DS was isolated for further complete structural characterization. Agarose-gel electrophoresis in combination with various enzymes, chondroitin ABC lyase, chondroitin B lyase, chondroitin ACII lyase from Arthrobacter aurescens, and chondroitin AC lyase from Flavobacterium heparinum, confirmed the DS nature of this polysaccharide. Furthermore, by evaluating the unsaturated disaccharides produced by the action of the various lyases, this natural polymer was found to be composed of approx. 75% of disaccharides containing iduronic acid (IdoA) mainly found in disaccharides monosulfated in position 4 of N-acetylgalactosamine (GalNAc) and disulfated in position 2 of the IdoA and 4 of GalNAc (disaccharide B typical of DS). In contrast, glucuronic acid was found to be mainly associated with the nonsulfated disaccharide (approx. 92%), while the rest formed low percentages of monosulfated disaccharides in position 4 or 6 of GalNAc preferentially located inside the chains. Generally, this GAG possesses a peculiar structure, due to the presence of significant amounts of nonsulfated disaccharide mainly located close to the nonreducing end, to the elevated percentage of the disaccharide B, and to the presence of not previously reported low amounts of the disaccharide monosulfated in position 2 of the uronic acid. S. inaequivalvis DS was also found to have a mean molecular mass of approx. 27,000 Da and a mean charge density of 1.10 that increases to 1.54 for the carbohydrate backbone composed of IdoA residues. (1)H-NMR and (13)C-NMR analyses confirmed the nature of S. inaequivalvis polymer revealed by the presence of signals related to DS corresponding to the residue of IdoA and GalNAc mainly sulfated at the C4 along with the presence of a signal belonging to the residue of H1 IdoA-2SO(4). S. inaequivalvis DS was further depolymerized by partial controlled digestion with chondroitinase ABC and separated into oligosaccharides by online HPLC/ESI-MS to obtain sequence information. The most prominent generated oligosaccharides comprised the repeating unit Delta Hex-GalNAcSO(4) thus confirming the results obtained by disaccharide analysis and the structures of the major oligosaccharides (from 6- to 10-mer) confirmed, by means of the LC-MS, the presence of approx. 20% of nonsulfated disaccharide. Furthermore, a minor but significant percentage of a monosaccharide having an m/z 300 and corresponding to GalNAcSO(4) belonging to the DS nonreducing end was observed along with saturated hexasaccharide derived from the nonreducing terminus of the intact DS ending with a uronic acid residue. Finally, S. inaequivalvis DS was calculated to possess a high heparin cofactor II activity of 169.2 +/- 10.7% fairly similar to that of several DS samples purified from porcine and bovine tissues.

Chondroitin sulfate and keratan sulfate are the major glycosaminoglycans present in the adult zebrafish Danio rerio (Chordata-Cyprinidae)

The zebrafish Danio rerio (Chordata-Cyprinidae) is a model organism frequently used to study the functions of proteoglycans and their glycosaminoglycan (GAG) chains. Although several studies clearly demonstrate the participation of these polymers in different biological and cellular events that take place during embryonic development, little is known about the GAGs in adult zebrafish. In the present study, the total GAGs were extracted from the whole fish by proteolytic digestion, purified by anion-exchange chromatography and characterized by electrophoresis after degradation with specific enzymes and/or by high-performance liquid chromatography (HPLC) analysis of the disaccharides. Two GAGs were identified: a low-molecular-weight chondroitin sulfate (CS) and keratan sulfate (KS), corresponding to approximately 80% and 20% of the total GAGs, respectively. In the fish eye, KS represents approximately 80% of total GAGs. Surprisingly, no heparinoid was detected, but may be present in the fish at concentrations lower than the limit of the method used. HPLC of the disaccharides formed after chondroitin AC or ABC lyase degradation revealed that the zebrafish CS is composed by DeltaUA-1-->3-GalNAc(4SO4) (59.4%), DeltaUA-1-->3-GalNAc(6SO4) (23.1%), and DeltaUA-1-->3-GalNAc (17.5%) disaccharide units. No disulfated disaccharides were detected. Immunolocalization on sections from zebrafish retina using monoclonal antibodies against CS4- or 6-sulfate showed that in the retina these GAGs are restricted to the outer and inner plexiform layers. This is the first report showing the presence of KS in zebrafish eye, and the structural characterization of CS and its localization in the zebrafish retina. Detailed information about the structure and tissue localization of GAGs is important to understand the functions of these polymers in this model organism.