Variations in Keratosulfates

Molecular and functional analysis of PmCHST1b in nacre formation of Pinctada fucata martensii

Keratan sulfate possesses considerable amounts of negatively charged sulfonic acid groups and participates in biomineralization. In the present study, we investigated characteristics and functions of a CHST1 gene identified from the pearl oyster Pinctada fucata martensii (PmCHST1b) which participated in the synthesis of keratan sulfate. PmCHST1b amino acid sequence carried a typical sulfotransferase-3 domain (sulfotransfer-3 domain) and belonged to membrane-associated sulfotransferases. Homologous analysis of CHST1 from different species showed the conserved motif (5' PSB motif and 3' PB motif) which interacted with 3'-phosphoadenosine-5'-phosphosulfate (PAPS). Structure analysis of sulfotransferase domain indicted that PmCHST1b showed the conserved catalytic structure character and the relationships presented in the phylogenetic tree conformed to that of traditional taxonomy. Expression pattern of PmCHST1b in different tissues and development stages showed that PmCHST1b widely expressed in all the detected tissues and development stages and showed the highest expression level in the central zone of mantle (MC). PmCHST1b expressed highly in the trochophore, D-stage larvae and spat which corresponded to prodissoconch and dissoconch shell formation, respectively. RNA interference (RNAi) successfully inhibited expression level of PmCHST1b in MC (P<0.05), and sulfate polymer content in the extrapallial fluid significantly reduced (P<0.05). Crystallization of shell nacre became irregular. Results above indicated that PmCHST1b may affect nacre formation by participating in synthesis of keratan sulfate in extrapallial fluid. This study provided fundamental materials for further research on the role of sulfotransferases and keratan sulfate in nacre formation.

Structural Characterization and Interaction with RCA120 of a Highly Sulfated Keratan Sulfate from Blue Shark (Prionace glauca) Cartilage

As an important glycosaminoglycan, keratan sulfate (KS) mainly exists in corneal and cartilage, possessing various biological activities. In this study, we purified KS from blue shark (Prionace glauca) cartilage and prepared KS oligosaccharides (KSO) through keratanase II-catalyzed hydrolysis. The structures of KS and KSO were characterized using multi-dimensional nuclear magnetic resonance (NMR) spectra and liquid chromatography-mass spectrometry (LC-MS). Shark cartilage KS was highly sulfated and modified with ~2.69% N-acetylneuraminic acid (NeuAc) through α(2,3)-linked to galactose. Additionally, KS exhibited binding affinity to Ricinus communis agglutinin I (RCA₁₂₀) in a concentration-dependent manner, a highly toxic lectin from beans of the castor plant. Furthermore, KSO from dp2 to dp8 bound to RCA₁₂₀ in the increasing trend while the binding affinity of dp8 was superior to polysaccharide. These results define novel structural features for KS from Prionace glauca cartilage and demonstrate the potential application on ricin-antidote exploitation.

Keratan sulfate, a complex glycosaminoglycan with unique functional capability

From an evolutionary perspective keratan sulfate (KS) is the newest glycosaminoglycan (GAG) but the least understood. KS is a sophisticated molecule with a diverse structure, and unique functional roles continue to be uncovered for this GAG. The cornea is the richest tissue source of KS in the human body but the central and peripheral nervous systems also contain significant levels of KS and a diverse range of KS-proteoglycans with essential functional roles. KS also displays important cell regulatory properties in epithelial and mesenchymal tissues and in bone and in tumor development of diagnostic and prognostic utility. Corneal KS-I displays variable degrees of sulfation along the KS chain ranging from non-sulfated polylactosamine, mono-sulfated and disulfated disaccharide regions. Skeletal KS-II is almost completely sulfated consisting of disulfated disaccharides interrupted by occasional mono-sulfated N-acetyllactosamine residues. KS-III also contains highly sulfated KS disaccharides but differs from KS-I and KS-II through 2-O-mannose linkage to serine or threonine core protein residues on proteoglycans such as phosphacan and abakan in brain tissue. Historically, the major emphasis on the biology of KS has focused on its sulfated regions for good reason. The sulfation motifs on KS convey important molecular recognition information and direct cell behavior through a number of interactive proteins. Emerging evidence also suggest functional roles for the poly-N-acetyllactosamine regions of KS requiring further investigation. Thus further research is warranted to better understand the complexities of KS.

Analytical method for determination of disaccharides derived from keratan sulfates in human serum and plasma by high-performance liquid chromatography/turbo-ionspray ionization tandem mass spectrometry

We established a highly sensitive LC/MS/MS method for the analysis of the disaccharides produced from keratan sulfates (KS). It was revealed that the disaccharides produced by keratanase II enzymatic digestion of KS could be determined with high sensitivity by negative ion mode of multiple reaction monitoring. Furthermore, monosulfated and disulfated disaccharides can be separated using a Hypercarb (2.0 mm i.d. x 150 mm, 5 microm) with a gradient elution of acetonitrile-0.01 m ammonium bicarbonate (pH 10). This method was applied to the determination of KS in serum and plasma of control subjects. The intra-day precision expressed as %CV was within 6.8% for five replicate analyses with three different control serum. The inter-day (overall, n = 15) precision was within 7.3% for three days. This method is sensitive, reproducible and would be useful for clinical analysis.

Matrix metalloproteinases and proteoglycans in axonal regeneration

After an injury to the adult mammalian central nervous system (CNS), a variety of growth-inhibitory molecules are upregulated. A glial scar forms at the site of injury and is composed of numerous molecular substances, including chondroitin sulfate proteoglycans (CSPGs). These proteoglycans inhibit axonal growth in vitro and in vivo. Matrix metalloproteinases (MMPs) can degrade the core protein of some CSPGs as well as other growth-inhibitory molecules such as Nogo and tenascin-C. MMPs have been shown to facilitate axonal regeneration in the adult mammalian peripheral nervous system (PNS). This review will focus on the various roles of proteoglycans and MMPs within the injured nervous system. First, we will present a general background on the injured central nervous system and explore the roles that proteoglycans play in the injured PNS and CNS. Second, we will discuss the various functions of MMPs within the injured PNS and CNS. Special attention will be paid to the possibility of how MMPs might modify the growth-inhibitory extracellular environment of the injured adult mammalian spinal cord and facilitate axonal regeneration in the CNS.

Localization of sulfated sialic acids in the dentinal tubules during tooth formation in mice

Lectin-like properties of the major enamel protein amelogenin suggest that it binds to glycoconjugates in dentinal tubules released at the dentin-enamel junction (DEJ) during enamel formation. Therefore, a detailed mapping of glycosylation in dentinal tubules during tooth formation was undertaken using histochemistry and lectin-binding assays. The tubular content exhibited sialidase-susceptible gamma-metachromasia with Toluidine Blue (pH 2.5) and staining with Alcian Blue (pH 1.0). The presence of sulfate groups was confirmed by benzidine reactions (Bracco-Curti's and tetrazonium assays). Alpha2,3-, alpha2,6- and alpha2,8-sialidases entirely abolished staining with the benzidine reactions. The presence of sialic acids in dentinal tubules was confirmed with the Bial's reaction and sialidase-susceptible binding of Limax flavus lectin suggesting that sialic acids are the major sulfated sugars in the glycoconjguates. Immunostaining with the monoclonal antibody 5-D-4 before and after treatment with chondroitin-4- and chondroitin-6-sulfatase confirmed the presence of keratan sulfate (KS), a sialylated proteoglycan, in dentinal tubules. We suggest that sulfated sialic acids are part of the KSs. The sulfated glycoconjugates are also found in dentin and the DEJ but not in predentin suggesting that amelogenin binds to the sialoconjugate during enamel formation.

Modification of di- and tetrasaccharides from shark cartilage keratan sulphate by refined anhydromethanolic hydrochloric acid-treatments and evaluation of their specific desulphation

Highly sulphated keratan di- and tetrasaccharides were prepared from keratan sulphate (KS) of shark cartilage by enzymatic digestion with keratanase II and subsequent chromatography. The tetrasaccharide fraction carrying four sulphate groups was completely desulphated by 100 mM anhydromethanolic hydrochloric acid (MeOH-HCl) treatment at room temperature for 16 h. The conditions for the desulphation reaction by MeOH-HCl treatment were examined using sulphated keratan di- and tetrasaccharides as substrates by means of reversed phase high performance liquid chromatography (HPLC) and/or capillary electrophoresis, followed by the preparation of partially desulphated keratan oligosaccharides. Sulphate substitution patterns of monosulphated keratan disaccharide and trisulphated keratan tetrasaccharide were evaluated by methylation analysis. The results suggested that 6-O-sulphate groups of Gal moieties are cleaved faster than those of GlcNAc moieties under the present conditions adopted for the MeOH-HCl treatment of KS-derived oligosaccharides.

Analytical method for keratan sulfates by high-performance liquid chromatography/turbo-ionspray tandem mass spectrometry

We established a highly sensitive LC/MS/MS method for the analysis of the disaccharides produced from keratan sulfates (KS). It was revealed that the disaccharides produced by keratanase II enzymatic digestion of KS could be determined with high sensitivity by the negative-ion mode of multiple reaction monitoring. Furthermore, monosulfated and disulfated disaccharides can be separated using a short column of Capcell Pak NH2 UG80 (35 mm x 2 mm i.d.). The complete analysis of one sample can be performed within 5 min. The assay method was validated and showed satisfactory sensitivity, precision, and accuracy, which enabled quantitation at subpicomole levels. From the results of analyses of KS obtained from cornea, nasal cartilage, and brain, it was found that the degree of sulfation at the C-6 position of the galactose residues differed among those samples in the following order: nasal cartilage > cornea > brain. Our analytical method is very useful for the analyses of KS in various biological materials and for comparison of the degree of sulfation of KS from various biological samples.

Keratan sulfate glycosaminoglycans in murine eosinophil-specific granules

We examined the presence of sialyl glycoconjugates in specific granules from murine bone marrow eosinophils. Lectin cytochemistry using Maackia amurensis lectin II (MAL II) specific for sialyl alpha-2,3 galactose residues demonstrated positive labeling in both immature and mature specific granules. Pretreatment with Clostridium neuraminidase or keratanase II eliminated the positive labeling of MAL II in the specific granules. High iron diamine-thiocarbohydrazide-silver proteinate physical development (HID-TCH-SP-PD) staining, which is specific for sulfated glycoconjugates, also positively labeled immature specific granules lacking crystalloids but not mature granules with crystalloids. Pretreatment with a combination of chondroitinase ABC and keratanase, or a combination of chondroitinase ABC and keratanase II, eliminated the positive labeling obtained with HID-TCH-SP-PD. These results indicate that the sialyl residues detected by MAL II are expressed as terminal sugar residues of keratan sulfate proteoglycan, which appears to be of the corneal type in view of its sensitivity to keratanase and keratanase II. (J Histochem Cytochem 47:481-488, 1999)

The structure of the keratan sulphate chains attached to fibromodulin isolated from articular cartilage

Fibromodulin has been isolated from bovine and equine articular cartilage and the attached keratan sulphate chains subjected to digestion by keratanase II. The oligosaccharides generated have been reduced and subsequently isolated by strong anion-exchange chromatography. Their structures have been determined by high-field 1H-NMR spectroscopy and high-pH anion-exchange chromatography. Both alpha(2-6)- and alpha(2-3)-linked N-acetylneuraminic acid have been found in the capping oligosaccharides, and, fucose which is alpha(1-3)-linked to N-acetylglucosamine has been found as a branch in both repeat region and capping oligosaccharides. These data demonstrate that there are fundamental differences between the structures present in the N-linked keratan sulphate chains attached to fibromodulin from articular cartilage and those from tracheal cartilage, which lack both alpha(2-6)-linked N-acetylneuraminic acid and alpha(1-3)-linked fucose. It has been confirmed that the keratan sulphate chains are short, being only eight or nine disaccharides in length. Very significant differences in the levels of galactose sulphation have been identified at the non-reducing end of the chain. The galactose residue adjacent to the non-reducing cap is sulphated in only 1-3% of chains, compared with a sulphation level of over 40% closer to the reducing end. This highlights the difference between the chain termini and the repeat region in terms of structure and points to the potential for functional importance. The repeat region and capping fragments of the N-linked keratan sulphates from bovine and equine articular cartilage fibromodulin have been found to have the following general structure: NeuAc-(alpha 2-3/6)Gal[6SO3-](beta 1-4)GlcNAc6SO3-(beta 1-3)Gal[6SO3-] (beta 1-4)¿[Fuc(alpha 1-3)]0-1GlcNAc6SO3-(beta 1-3)Gal-[6SO3-](beta 1-4)¿ 6-7GlcNAc6SO3-.

Multiple non-reducing chain termini isolated from bovine corneal keratan sulfates

Keratan sulfate-containing proteoglycans were isolated from bovine cornea (15-month-old to 3-year-old animals) and digested with the enzyme, keratanase II. The released oligosaccharides, which included non-reducing termini and repeat region oligosaccharides but not linkage regions, were reduced with alkaline borohydride and fractionated on a Spherisorb column. These oligosaccharides were examined by 600-MHz 1H NMR spectroscopy using one- and two-dimensional methods and, in addition to some oligosaccharide alditols previously recovered from skeletal keratan sulfate, the following new capping structures were identified: NeuAcalpha2-6Galbeta1-4GlcNAc(S)-ol, NeuAcalpha2-3Gal(S)beta1-4GlcNAc(S)beta1-3Galbeta1-4GlcNAc(S )-ol, NeuGcalpha2-6Galbeta1-4GlcNAc(S)beta1-3Galbeta1-4Gl cNA c(S)-ol, NeuGcalpha2-3Galbeta1-4GlcNAc(S)beta1-3Galbeta1-4Gl cNA c(S)-ol, NeuGcalpha2-3Gal(S)beta1-4GlcNAc(S)beta1-3Galbeta1-4GlcNAc(S )-ol, NeuGcalpha2-3Gal(S)beta1-4GlcNAc(S)beta1-3Gal(S)beta1-4GlcNAc(S)-o l, Galalpha1-3Galbeta1-4GlcNAc(S)beta1-3Galbeta1-4GlcNAc( S)-ol, Galalpha1-3Galbeta1-4GlcNAc(S)beta1-3Gal(S)beta1-4GlcNAc(S)- ol, GlcNAc(S)beta1-3Gal(S)beta1-4GlcNAc(S)-ol, and GalNAc(S)beta1-3Gal(S)beta1-4GlcNAc(S)-ol. These structures represent seven families of capping residues, whose relative molar proportions are given in parentheses: NeuAcalpha(2-3)- (12%), NeuAcalpha(2-6)- (41%), NeuGcalpha(2-3)- and NeuGcalpha(2-6)- families (12%), Galalpha(1-3)- (26%), GalNAc(S)beta(1-3)- (5%), and GlcNAc(S)beta(1-3)- (4%). It is not clear, at present, where each of these structures occurs on the bi-antennary N-linked corneal keratan sulfate chains, which themselves occur within three keratan sulfate proteoglycan species. However, examination of the relative proportions of the capping to the repeat structures and knowledge of the average molecular size suggests that the sum of these non-reducing termini represents the caps of two antennae.

Transport of UDP-galactose into the Golgi lumen regulates the biosynthesis of proteoglycans

The lumen of the Golgi apparatus is the subcellular site where galactose is transferred, from UDP-galactose, to the oligosaccharide chains of glycoproteins, glycolipids, and proteoglycans. The nucleotide sugar, which is synthesized in the cytosol, must first be transported into the Golgi lumen by a specific UDP-galactose transporter. Previously, a mutant polarized epithelial cell (MDCKII-RCAr) with a 2% residual rate of transport of UDP-galactose into the lumen of Golgi vesicles was described (Brandli, A. W., Hansson, G. C., Rodriguez-Boulan, E., and Simons, K. (1988) J. Biol. Chem. 263, 16283-16290). The mutant has an enrichment in glucosyl ceramide and cell surface glycoconjugates bearing terminal N-acetylglucosamine, as well as a 75% reduction in sialylation of cell surface glycoproteins and glycosphingolipids. We have now studied the biosynthesis of galactose containing proteoglycans in this mutant and the corresponding parental cell line. Wild-type Madin-Darby canine kidney cells synthesize significant amounts of chondroitin sulfate, heparan sulfate, and keratan sulfate, while the above mutant synthesizes chondroitin sulfate and heparan sulfate but not keratan sulfate, the only proteoglycan containing galactose in its glycosaminoglycan polymer. The mutant also synthesizes chondroitin 6-sulfate rather than only chondroitin 4-sulfate as wild-type cells. Together, the above results demonstrate that the Golgi membrane UDP-galactose transporter is rate-limiting in the supply of UDP-galactose into the Golgi lumen; this in turn results in selective galactosylation of macromolecules. Apparently, the Km for galactosyltransferases involved in the synthesis of linkage regions of heparan sulfate and chondroitin sulfate are significantly lower than those participating in the synthesis of keratan sulfate polymer, glycoproteins, and glycolipids. The results also suggest that the 6-O-sulfotransferases, in the absence of their natural substrates (keratan sulfate) may catalyze the sulfation of chondroitin 4-sulfate as alternative substrate.

N- and O-linked keratan sulfate on the hyaluronan binding region of aggrecan from mature and immature bovine cartilage

In the hyaluronan binding region (HABR) peptide of aggrecan, there is a marked increase in the level of keratan sulfate (KS) during aging. To determine the sites of KS attachment, KS-containing peptides were prepared from HABRs from immature and mature bovine articular cartilage by digestion with trypsin or papain followed by carbohydrate analysis and peptide sequencing. KS is attached to Thr42 within loop A in mature, but not in immature, HABR. Within loop B KS is N-linked to Asn220 in both HABRs, but in the immature HABR the chains are shorter. Asn314 in loop B' of mature HABR is substituted either with a KS chain or with an oligosaccharide of the complex type. In immature HABR this site does not carry KS. In the interglobular domain, 2 threonine residues within the sequence TIQTVT are substituted in both calf and steer, and in steer further substitution occurs within the sequence NITEGEA, which contains a major catabolic cleavage site (Sandy, J., Neame, P.J., Boynton, R., and Flannery, C.R. (1991) J. Biol. Chem. 266, 8683-8685). The extreme polydispersity of mature HABR was investigated by preparing four subfractions of increasing molecular size which had essentially the same protein core, i.e. Val1-Arg367 or Val1-Arg375. The smaller species lacked the KS chains attached to loop A. These results show that KS substitution occurs within each of the disulfide-bonded loops of the HABR, that the KS may be either N- or O-linked, and that variations in the addition of KS are responsible for the polydispersity of mature HABR.

Oligosaccharides derived by keratanase II digestion of bovine articular cartilage keratan sulphates

Alkaline borohydride-reduced keratan sulphate chains from bovine articular cartilage (6-8-year-old animals) were subjected to a limit digest with the enzyme keratanase II. Using 1H-NMR spectroscopy, 25 reduced oligosaccharides deriving from keratan sulphate were shown to have the following structures [GlcNAc(6S)-ol represents N-acetylglucosaminitol 6-O-sulphate]: Gal beta 1-4-GlcNAc(6S)-ol, Gal beta 1-4GlcNAc(6S)beta 1-3Gal beta 1-4GlcNAc(6S)-ol, Gal(6S)beta 1-4GlcNAc(6S)-ol, Gal-(6S)beta 1-4GlcNAc(6S) beta 1-3Gal beta 1-4GlcNAc(6S)-ol, Gal beta 1-4GlcNAc(6S)beta 1-3Gal(6S)beta 1-4GlcNAc(6S)-ol, Gal(6S)beta 1-4GlcNAc(6S)beta 1-3Gal(6S)1-4GlcNAc(6S)-ol, Gal beta 1-4(Fuc alpha 1-3)GlcNAc(6S)-ol, Gal beta 1-4-(Fuc alpha 1-3)GlcNAc(6S)beta1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc(6S)-ol, Gal beta 1-4GlcNAc(6S)beta 1-3Gal beta 1-4(Fuc alpha 1-3)-GlcNAc(6S)-ol, Gal beta 1-4(Fuc alpha 1-3)GlcNAc(6S)beta 1-3Gal beta 1-4GlcNAc(6S)-ol, Gal(6S) beta 1-4GlcNAc-(6S)beta 1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc(6S)-ol, Gal beta 1-4(Fuc alpha 1-3)GlcNAc(6S)beta 1-3Gal(6S)1-4GlcNAc(6S)-ol, Gal beta 1-4GlcNAc(6S)beta 1-6(Gal beta 1-3)GalNAc-ol, Gal beta 1-4GlcNAc(6S) beta1-6(NeuAc2-3Gal beta 1-3)Gal-NAc-ol, Gal beta 1-4GlcNAc(6S)beta 1-3Gal beta 1-4GlcNAc(6S)beta 1-6(Gal beta 1-3) GalNAc-ol, Gal(6S)beta 1-4GlcNAc-(6S)beta 1-6(Gal beta 1-3)GalNAc-ol, Gal beta 1-4GlcNAc(6S)beta 1-3Gal beta 1-4GlcNAc(6S)beta 1-6(NeuAc2-3Gal beta 1-3)-GalNAc-ol, Gal(6S)beta 1-4GlcNAc(6S)beta 1-6(NeuAc alpha 2-3Gal beta 1-3)GalNAc-ol, Gal(6S) beta 1-4GlcNAc-(6S)beta 1-3Gal beta 1-4GlcNAc(6S)beta 1-6(Gal beta 1-3)GalNAc- ol, Gal(6S)beta 1-4GlcNAc(6S)beta 1-3Gal beta 1-4GlcNAc-(6S)beta 1-6(NeuAc alpha 2-3Gal beta 1-3)GalNAc-ol, NeuAc alpha 2-6Gal beta 1-4GlcNAc(6S)beta 1-3Gal beta 1-4GlcNAc(6S)-ol, NeuAc alpha 2-3Gal beta 1-4GlcNAc(6S)beta 1-3Gal beta 1-4GlcNAc(6S)-ol, NeuAc alpha 2-6Gal beta 1-4GlcNAc(6S)beta 1-3Gal-(6S)beta 1-4GlcNAc(6S)-ol, NeuAc alpha 2-3Gal beta 1-4GlcNAc(6S)beta 1-3Gal(6S)beta 1-4GlcNAc(6S)-ol and Neu-Ac alpha 2-3Gal(6S)beta 1-4GlcNAc(6S)beta 1-3Gal(6S beta)1-4GlcNAc(6S)-ol. Proton chemical shifts for these oligosaccharides were assigned using one- and two-dimensional NMR spectroscopic methods. These results confirm the findings of Nakazawa et al. [Nakazawa, K., Ito, M., Yamagata, T. and Suzuki, S. (1989) in Keratan sulphate: chemistry, biology and chemical pathology (Greiling, H. and Scott, J.E., eds) pp. 99-110, The Biochemical Society, London], namely that keratanase II cleaves the O-glycosidic bond of a beta(1-3)-linked 6-O-sulphated N-acetylglucosamine.(ABSTRACT TRUNCATED AT 400 WORDS)

Monoclonal antibodies to the large chondroitin sulphate proteoglycan from bovine temporomandibular joint disc

Four hybrid cell lines producing monoclonal antibodies (designated AC2, AH12, DB10 and DD11) were derived from mice immunized with the large chondroitin sulphate proteoglycan isolated and purified from the bovine temporomandibular joint disc. The epitopes were partially characterized by enzyme-linked immunosorbent assays and staining patterns on immunoblots of intact proteoglycans and digests made with glycosidases and proteinases. All four monoclonal antibodies appeared to recognize some form of keratan sulphate although the epitopes for two (AC2 and DD11) were probably identical. One antibody (AH12) showed almost no reactivity with corneal keratan sulphate but stained a small keratan sulphate proteoglycan extracted from the disc, in addition to the large chondroitin sulphate proteoglycan. These antibodies were used for immunohistochemical staining of sections of the disc and showed that keratan sulphate associated with the large chondroitin sulphate proteoglycan was concentrated inside and away from the periphery of the structure but close to the inferior and superior surfaces, in a pattern which may reflect the adaptation of the extracellular matrix to the mechanical stresses placed on it by mastication.

A full assignment of proton resonances for an alpha(1-3)-linked fucose residue in keratan sulphate from bovine articular cartilage

Full proton NMR assignments have been achieved for the alpha(1-3)-linked fucose residues contained in alkaline borohydride reduced keratan sulphate chains derived from bovine articular cartilage. This involved 500 MHz spectroscopy at 60 degrees C and included COSY and RELAYED-COSY determinations.

The quantitative discrimination of corneal type I, but not skeletal type II, keratan sulfate in glycosaminoglycan mixtures by using a combination of dimethylmethylene blue and endo-beta-D-galactosidase digestion

The quantitation of individual glycosaminoglycans in mixtures of polyanions using the dimethylmethylene blue (DMB) method described by R. W. Farndale, D. J. Buttle, and A. J. Barrett (1986, Biochim. Biophys. Acta 883, 173) is dependent on enzymatic hydrolysis by specific polysaccharidases. While using this method to examine the keratan sulfate (KS) of the intervertebral disc we found that digestion with commercially available keratanase decreased binding to DMB by less than 30%, whereas corneal KS was reduced by 85%. However, by preincubating the KS fractions with endo-beta-D-galactosidase prior to keratanase treatment the corneal KS could be completely digested and disc KS digestion increased to 60%. It is suggested that the resistance of the disc KS to these digestive procedures arises from branching and/or sites of multisulfation on the polysaccharide chain. Agarose gel electrophoresis and compositional analyses of the keratan sulfates supported such an interpretation.

Isolation and partial characterization of a novel keratan sulfate proteoglycan from metamorphosing bonefish (Albula) larvae

Proteoglycans (PGs) were isolated from leptocephalous larvae of the bonefish (Albula sp.), which were in the early stages of metamorphosis, using both associative and dissociative conditions in the presence of protease inhibitors. The procedure was rapid and resulted in an extraction efficiency of 75% (associative) and 85-90% (dissociative). The majority of co-extracted protein could be effectively separated from the PGs by utilizing either Sepharose CL-2B or CL-6B gel chromatography. Sepharose CL-2B chromatography of extracted PGs after treatment with bacterial keratan sulfate-endo-β-galactosidase (keratanase) showed that most of the high molecular weight (M r) carbohydrate was degraded. Free keratan sulfate (KS) chains were prepared from whole-larva extracts (which also contain small amounts of chondroitin sulfate) by both chondroitinase ABC treatment and ethanol fractionation. Sepharose CL-6B chromatography under dissociative conditions showed that larval KS chains were much larger (M r∼55,000) than those from cornea. These chains tended to aggregate when chromatographed under associative conditions. Larval KS was degraded by keratanase and resistant to chondroitinase, ABC and testicular hyaluronidase. Differences were also noted in the oligosaccharides produced by keratanase treatment of the two preparations. However, biochemical composition of larval and corneal KS was similar.

Mucopolysaccharidases from Pseudomonas sp. Isolation and partial characterization of constitutive enzymes involved in the degradation of keratan sulfate and chondroitin sulfate

Four constitutive enzymes, capable of degrading keratan sulfate, were isolated from Pseudomonas sp.: a particulate endoglycosidase, a soluble endoglycosidase, a soluble exo-beta-D-galactosidase and a soluble exo-beta-D-N-acetylglucosaminidase. The endoglycosidases were shown to act only upon keratan sulfate forming beta-D-2-acetamido-2-deoxy-6-O-sulfoglucosyl-(1----3)-D-galactose, as the main product. This results indicates that the enzyme catalyses the hydrolysis of beta-D-galactose-(1----4)-N-acetylglucosamine linkages. It was also shown that this monosulfated disaccharide inhibits the particulate keratan sulfate endoglycosidase. The bovine nucleus pulposus keratan sulfate is depolymerized at a lower rate and extent when compared to the corneal keratan sulfate. The soluble endoglycosidase is very labile, in contrast to the particulate enzyme, which has been stored at -20 degrees C or at 4 degrees C for at least 12 months with no loss in activity. The particulate endoglycosidase and the soluble exo-beta-D-galactosidase and exo-beta-D-N-acetylglucosaminidase are induced when the bacteria is grown in adaptative media containing either 0.1% keratan sulfate or 0.1% chondroitin sulfate. Furthermore, particulate forms of the exoenzymes were detected. The soluble endoglycosidase specific activity, in contrast, is approximately the same in extracts of cells grown in glucose, keratan sulfate or chondroitin sulfate. A chondroitin sulfate lyase was also identified in the soluble extracts of Pseudomonas sp. cells. This enzyme depolymerizes chondroitin 4-sulfate, chondroitin 6-sulfate and hyaluronic acid forming unsaturated disaccharides as main products. It is also active upon the glucuronic-acid-containing regions of the dermatan sulfate molecules. The properties of the soluble enzymes, further purified by ion-exchange chromatography, and of the particulate keratan sulfate endoglycosidase are presented.

The period clock locus of D. melanogaster codes for a proteoglycan

The period (per) gene of D. melanogaster is involved in the generation of biological rhythms. The most striking feature of the predicted coding sequence, corresponding to the key 4.5 kb transcript from this locus, is an extensive run of alternating Gly-Thr residues. This is homologous to a series of Gly-Ser repeats in a chondroitin sulfate proteoglycan. To determine whether the per transcript codes for a proteoglycan, a region of its coding sequence was expressed (in bacteria) as part of a fusion protein, which was used to immunize rabbits. When the resultant immune sera were used to probe fly protein preparations, they detected an antigen that is present in wild-type flies and absent in a per- mutant. Biochemical characterization of this antigen indicated that it is indeed a proteoglycan.

Isolation and characterization of sulphated oligosaccharides released from bovine corneal keratan sulphate by the action of endo-beta-galactosidase

A series of oligosaccharides has been isolated from the keratan sulphate peptidoglycan (3 M NaCl fraction) of bovine cornea after digestion with the endo-beta-galactosidase of Bacteroides fragilis. Structural information on the major oligosaccharides was obtained from (a) their susceptibilities to endo-beta-galactosidase before and after desulphation, (b) their elution positions on a column of Bio-Gel P-4 and retention times on a high-performance anion-exchange column and (c) negative-ion fast-atom-bombardment mass spectrometry. More than 75% of the oligosaccharides were sulphated unbranched poly(N-acetyllactosamine) sequences, (-3/4GlcNAc beta 1-3Gal beta 1-)n, and approximately 3% was the neutral disaccharide, GlcNAc beta 1-3Gal. The sulphated disaccharide, GlcNAc-SO-3 beta 1-3Gal, accounted for almost 35% of the oligosaccharide material while 40% consisted of four oligosaccharides, unbranched tetra-, hexa-, octa- and decasaccharides of poly(N-acetyllactosamine) type, having 3, 5, 7 and 9 sulphate residues respectively. Proton nuclear magnetic resonance studies at 500 MHz (Hounsell, E. F., et al. following paper in this journal) have shown that a sulphate residue is attached to the C-6 position of each N-acetylglucosamine and each internal galactose residue of these four oligosaccharides which express to varying degrees the antigenic determinants recognised by three monoclonal antibodies to keratan sulphate (Mehmet, H. et al., paper which follows the next paper in this journal).

The effect of digestion with keratanase (Pseudomonas sp.) on certain histochemical reactions for glycosaminoglycans in cartilaginous and corneal tissues

The effect of digestion with keratanase (Pseudomonas sp.) on the Alcian Blue (AB) pH 1.0, pH 2.5, Aldehyde Fuchsin, high iron diamine, low iron diamine and dialysed iron-ferrocyanide reactions has been tested in the costal and ear cartilage tissues of the rabbit and corneal tissues of the rat and rabbit. The effect of digestion with chondroitinases ABC and AC on the same reactions was examined in the same tissues for comparison. Digestion with keratanase diminished the intensity of all the reactions in the cartilage tissues to a variable extent; however, the diminutions in intensity of the reactions appeared to be less marked as compared with those following digestion with two chondroitinases. In the corneal stroma, all the reactions were markedly reduced in intensity following digestion with keratanase. In contrast, these reactions were only slightly or moderately diminished in intensity by digestion with the two chondroitinases. As glycosamino-glycans are known to be present in cartilage and corneal tissues and the substrate specificities of the three enzymes used are now well established, the present results are consistent with the concept that keratanase specifically degrades and releases keratan sulphates involved in the tissues.

Immunological methods for the detection and determination of connective tissue proteoglycans

In this paper we report the use of immunological methods for specifically detecting and determining proteoglycan in cartilage and other connective tissues. Antibodies (polyclonal and monoclonal) have been raised against specific components of cartilage proteoglycan aggregates (i.e., proteoglycan monomer and link protein). Radioimmunoassay procedures and immunohistochemical procedures have been developed and used to demonstrate the occurrence of cartilage-like proteoglycan and link protein in bovine aorta. Similarly, immunofluorescent studies have been used to analyze proteoglycan distribution in skin. Using antibodies specific for chondroitin-4-sulfated proteoglycan, their presence was demonstrated in dermal connective tissue and connective tissue surrounding nerve and muscle sheaths. However, chondroitin-4-sulfated proteoglycan was completely absent in the epidermis of skin and areas surrounding invaginating hair follicles. These immunological procedures are currently being used to complement conventional biochemical analyses of proteoglycans found in different connective tissue matrices.

Studies on the characterization of the linkage-region between polysaccharide chain and core protein in bovine corneal proteokeratan sulfate

1) A new method of enrichment of the linkage-region in corneal proteokeratan sulfate is described, which consists of desulfation of peptidokeratan sulfate, followed by chromatography on Con A-Sepharose 4B and enzymatic degradation with beta-D galactosidase and beta-N-acetyl-D-glucosaminidase. 2) After permethylation, hydrolysis, reduction with sodium borohydrid and acetylation gas chromatography/mass spectrometry analyses were performed. The followings products could be detected as their peracetates: 2,3,4-tri-O-methylfucitol; 2,3,4,6-tetra-O-methylmannitol; 3,4,6-tri-O-methylmannitol; 2,4-di-O-methylmannitol; 2,3,4,6-tetra-O-methylgalactitol; 2,4,6-tri-O-methylgalactitol; 2,4-di-O-methylgalactitol. 3) The results point to the presence of a branched linkage region in the proteokeratan sulfate molecule with one mannose as the branching point and two mannose residues as the starting point of two disaccharide chains.

Skeletal keratan sulfate from different tissues. Characterization and alkaline degradation

Keratan sulfate-rich peptides were isolated after digestion of proteoglycans from bovine nasal cartilage and bovine nucleus pulposus with chondroitinase ABC, trypsin and chymotrypsin. The keratan sulfate enriched peptides from nucleus pulposus were larger than those from nasal cartilage. Keratan sulfate chains were isolated after treatment of the keratan sulfate-rich peptides under alkaline, reductive conditions. Proteoglycans from nucleus pulposus contain longer keratan sulfate chains, as is shown primarily by gel chromatography of the keratan sulfate-rich peptides and the keratan sulfate chains, but also from end-group analyses of the keratan sulfate chains.

Isolation and partial characterization of proteoglycans from sheep lung parenchyma

Greater than 90% of the proteoglycans of sheep lung parenchyma, as measured by uronic acid, were solubilized employing a sequential procedure with guanidine hydrochloride, dithiothreitol and Triton X-100. The amounts solubilized were 68.7%, 16.2% and 5.9%, respectively. The guanidine hydrochloride extract was chromatographed using DEAE-cellulose in urea and eluted with increasing concentrations of NaCl. A major fraction (containing a 6.5-fold enrichment of uronic acid) was obtained with 0.5 M NaCl and further purified by Sepharose Cl-6B chromatography in guanidine hydrochloride. To demonstrate the presence of protein-linked glycosaminoglycans, the void volume peak containing protein and uronic acid was digested with papain and rechromatographed. Evidence for the presence of proteoglycans was obtained by observing an almost complete loss of uronic acid in the void volume and the appearance of a uronic acid peak in the included volume, migrating in the same area as single-chain glycosaminoglycans. Electrophoretic migration and disappearance of bands in electrophoresis after digestion with specific mucopolysaccharide lyases indicated that the small amount of uronic acid remaining in the void volume was hyaluronic acid whereas the included volume contained hyaluronic acid, heparan sulfate, chondroitin sulfates and/or dermatan sulfate.

Chondroitinase-resistant sulfated glycosaminoglycans synthesized by cartilages of chick embryos and of newborn chickens and rats

Biosynthesis of chondroitinase-resistant glycosaminoglycans as minor components was studied in the cartilages of chick embryos and of newborn chickens and rats. Sternal and knee cartilages were labeled in vitro with 35SO42-, and then 35S-labeled glycosaminoglycans were analyzed. In rats up to 2 weeks old, only one glycosaminoglycan could be detected as heparan sulfate. In the chick embryos and the newborn chickens, however, keratan sulfate as well as heparan sulfate could be detected. As chondroitinase-sensitive glycosaminoglycans, large amounts of both chrondroitin 4- and 6-sulfates were synthesized in the chick cartilage, but the synthesis of chondroitin 6-sulfate could scarcely be seen in the rat cartilage. The results seem to indicate that the biosynthesis of keratan sulfate has some relation to that of chondroitin 6-sulfate.

Abnormal keratan sulphate excretion

Simple methods for the detection of keratan sulphate in urine have been applied to over 300 urine samples collected from children and adults with bone and cartilage dysplasias with or without mental retardation. Abnormal keratan sulphate excretion, which is a feature of type IV mucopolysaccharidosis (Morquio syndrome), is found in patients with that condition only during childhood. Abnormal excretion is also a feature of Kniest dysplasia and GM1 gangliosidosis and may be present in a number of other bone and cartilage dysplasias of unknown aetiology.

Galactose-6-sulfatase from Actinobacillus sp. IFO-13310 and its action on sulfated oligosaccharides from keratan sulfate

A 6-sulfatase specific for sugasr of the galactose configuration was purified 81-fold from the crude extract of Actinobacillus sp. IFO-13310. This preparation contained activity towards both N-acetylgalactosamine 6-sulfate and galactose 6-sulfate (relative activity, 2.4 : 1). The enzyme also release inorganic sulfate from the non-reducing galactose 6-sulfate end group of a trisaccharide disulfate prepared from keratan sulfate by sequential degradation with endo-beta-galactosidase, N-acetylglucosamine-6-sulfatase and exo-beta-N-acetylglucosaminidase. In addition, a tetrasaccharide trisulfate bearing the non-reducing N-acetylglucosamine 6-sulfate end group, also enzymatically prepared from keratan sulfate, was degraded to give rise to inorganic sulfate, N-acetylglucosamine and galactose by the sequential action of this enzyme, N-acetylglucosamine-6-sulfatase, exo-beta-N-acetylglucosaminidase and exo-beta-galactosidase (Charonia lampas).

Biochemical changes in progressive osteoarthrosis

Quantitative and qualitative variations in glycosaminoglycan content were studied in fibrillated, intact, and osteophytic cartilage of the human femoral head in osteoarthrosis. Total glycosaminoglycan content was reduced in fibrillated, unchanged in intact, and raised in osteophytic cartilage. In fibrillated and osteophytic cartilage the ratio of chondroitin sulphate to keratan sulphate was high and therefore resembled immature cartilage. Hyaluronic acid was present in reduced amount in all osteoarthrotic material. Proportionally more proteoglycans were extractable by 0-15 M NaCl and 4 M guanidinium chloride from the diseased cartilage than from normal cartilage, and all proteoglycans irrespective of buoyant density were carbohydrate deficient. It is postulated that the changes described are compatible with collagen and matrix disruption due to focal overloading and the general attempt at repair.