Characterizing the electrospray-ionization mass spectral fragmentation pattern of enzymatically derived hyaluronic acid oligomers

Mass spectrometric investigations of the action of hypochlorous acid on monomeric and oligomeric components of glycosaminoglycans

Hypochlorous acid (HOCl) is a strong non-radical oxidant, which is generated during inflammatory processes under the catalysis of the enzyme myeloperoxidase (MPO). HOCl reacts particularly with sulfhydryl and amino acid residues but affects also many other biomolecules. For instance, the glycosaminoglycans of articular cartilage and synovial fluids (such as hyaluronan) undergo degradation in the presence of HOCl at which the native polysaccharide is fragmented into oligosaccharides in a complex reaction. This is an initial mass spectrometry (MS)-based investigation dealing with the HOCl-induced degradation of glycosaminoglycans and the conversion of the related monosaccharides into chlorinated products. In particular, it will be shown that the reaction between HOCl and hyaluronan is slower than originally assumed and results in the generation of different products (particularly the hyaluronan monosaccharides) by the cleavage of the β-1,3/1,4-glycosidic linkages. The MS detection of chlorinated products is, however, only possible in the case of the monosaccharides. Potential reasons will be discussed.

Insights into structure, affinity, specificity, and function of GAG-protein interactions through the chemoenzymatic preparation of defined sulfated oligohyaluronans

High amounts of glycosaminoglycans (GAG) such as hyaluronan (HA) occur in connective tissues. There is nowadays increasing evidence that a "sulfation code" exists which mediates numerous GAG functions. High molecular weight and inhomogeneity of GAG, however, aggravated detailed studies. Thus, synthetic oligosaccharides were urgently required. We will review here chemoenzymatic and analytic strategies to provide defined sulfated and anomerically modified GAG oligosaccharides of the HA type. Representative studies of protein/GAG interactions by (bio)chemical and biophysical methods are reported yielding novel insights into GAG-protein binding. Finally, the biological conclusions and in vivo applications of defined sulfated GAG oligosaccharides will be discussed.

Qualitative and quantitative analysis of hyaluronan oligosaccharides with high performance thin layer chromatography using reagent-free derivatization on amino-modified silica and electrospray ionization-quadrupole time-of-flight mass spectrometry coupling on normal phase

Purified oligomers of hyalobiuronic acid are indispensable tools to elucidate the physiological and pathophysiological role of hyaluronan degradation by various hyaluronidase isoenzymes. Therefore, we established and validated a novel sensitive, convenient, rapid, and cost-effective high performance thin layer chromatography (HPTLC) method for the qualitative and quantitative analysis of small saturated hyaluronan oligosaccharides consisting of 2-4 hyalobiuronic acid moieties. The use of amino-modified silica as stationary phase allows a simple reagent-free in situ derivatization by heating, resulting in a very low limit of detection (7-19 pmol per band, depending on the analyzed saturated oligosaccharide). By this derivatization procedure for the first time densitometric quantification of the analytes could be performed by HPTLC. The validated method showed a quantification limit of 37-71 pmol per band and was proven to be superior in comparison to conventional detection of hyaluronan oligosaccharides. The analytes were identified by hyphenation of normal phase planar chromatography to mass spectrometry (TLC-MS) using electrospray ionization. As an alternative to sequential techniques such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), the validated HPTLC quantification method can easily be automated and is applicable to the analysis of multiple samples in parallel.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2003-2004

This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.

Chondroitin C lyase [4.2.2.] is unable to cleave fructosylated sequences inside the partially fructosylated Escherichia coli K4 polymer

Chondroitin C lyase was demonstrated to be unable to act on fructosylated sequences inside a partially fructosylated polysaccharide having the chondroitin backbone structure, the Escherichia coli K4 polymer, using different analytical approaches. Chondroitin C lyase produced various unsaturated oligosaccharides by acting on an approximately 27%-fructosylated K4 polymer. The online HPLC-ESI-MS approach showed the disaccharide nature of the main species produced by chondroitinase C as DeltaHexA-GalNAc. Furthermore, the non-digested sequences inside the K4 polymer were demonstrated to be oligosaccharides bearing a fructose for each glucuronic acid unit. In fact, unsaturated fully fructosylated oligomers, from tetrasaccharide to decasaccharide (DeltaHexA(Fru)-GalNAc-[GlcA(Fru)-GalNAc](n) with n between 1 and 4), at decreasing percentages, were produced by the enzyme. These results clearly indicate that chondroitinase C cleaved the innermost glucuronic acid-N-acetylgalactosamine linkage without affecting the 1,4 glycosidic linkage between fructosylated glucuronic acid and N-acetylgalactosamine residues, confirming that the 3-O-fructosylation of the GlcA residue renders the polysaccharide resistant to the enzyme action. This novel specific activity of chondroitinase C was also useful for the production of discrete microgram amounts of fully fructosylated oligomers, from 4- to 10-mers, from E. coli K4 for possible further studies and applications.

On-line HPLC/ESI-MS separation and characterization of hyaluronan oligosaccharides from 2-mers to 40-mers

A new method for the separation and identification of oligosaccharides obtained by enzymatic digestion of hyaluronic acid (HA) with hyaluronidase (EC 3.2.1.35) using on-line high-performance liquid chromatography/electrospray mass spectrometry (HPLC/ESI-MS) is presented. Reversed-phase ion pairing-HPLC, based on tributylamine salts and a volatile mobile phase, provided excellent chromatographic resolution and separation was achieved for HA oligosaccharides containing 2-40 monomers (from 2- to 40-mers). Using the on-line ion trap mass analyzer, complete identification and structural information for each HA oligomer species was obtained. In particular, a series of negatively charged species of different m/z ratios are seen for each oligosaccharide. Smaller HA species, from 2- to 4-mers, exhibit mainly [M-H](-1) anions, whereas the 6-10-mers exist predominantly as the charge state of -2. The HA oligomers from 12- to 18-mers are mainly represented by [M-3H](-3) anions while species from 20- to 28/30-mers are characterized by a charge state of -4. HA oligosaccharides from 32- to 40-mers exist as [M-5H](-5) anions. Furthermore, for smaller HA species, from 4/6- to 18/20-mers, ESI-MS revealed, generally in low relative abundance, anions related to the loss of one/two monosaccharide unit(s) from the oligomers, and no odd-numbered anions were produced for HA species greater than 20-mers.

Mass spectrometry characterization of Escherichia coli K4 oligosaccharides from 2-mers to more than 20-mers

The separation and characterization of oligosaccharides obtained by hyaluronidase [E.C. 3.2.1.35] digestion of Escherichia coli K4 polysaccharide using online high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) are presented. Complete identification and structural information for oligosaccharides containing 2-24 monomers (from 2- to 24-mers) were obtained. In particular, smaller K4 species, from 2-mers to 4-mers, exhibited mainly [M-H](-1) anions, whereas the 6- to 8-mers existed predominantly at the charge state of -2. The K4 oligomers from 10-mers to 14-mers were mainly represented by [M-3H](-3) anions while species from 16- to 20-mers were characterized by a charge state of -4. K4 oligosaccharides from 22- to 24-mers existed as [M-4H](-4) and [M-5H](-5) anions and, for this latter species, ions having a charge state of -6 appeared. For smaller K4 species, in particular from 6-mers to 10-mers, ESI-MS revealed anions related to the loss of one monosaccharide unit from the oligomers due to apparent collisional activation and ion source fragmentation. However, no odd-numbered anions were produced for K4 2/4-mer species or for oligosaccharides greater than 12-mers, while for K4 species 8/10-mer, ESI-MS revealed odd-numbered anions generally in low relative abundance making the interpretation of the spectra easier. The ESI-MS spectra of oligosaccharides separated by online HPLC were applied to the evaluation of the K4 polymerization process, confirming that the addition of fructose units is not critical for chain elongation as variously fructosylated oligomer species were detected directly on the K4 carbohydrate backbone.

Enzymatic and chemical methods for the generation of pure hyaluronan oligosaccharides with both odd and even numbers of monosaccharide units

Hyaluronan oligosaccharides display physiological activities not associated with the polymer and are widely used to characterize hyaluronan-binding proteins. They can also be used as biocompatible starting blocks for chemical derivatization. Here we present methods for generating milligram quantities of unusual odd- and even-numbered oligosaccharides, greatly increasing the diversity of reagents for use in such studies. These methods are based upon protocols from the 1960s, at which time it was very difficult to assess the stereochemical purity of the products. To address this, products were analyzed with modern high-field nuclear magnetic resonance spectroscopy. Alkaline beta-elimination conditions previously used to remove reducing-terminal N-acetylglucosamine residues in fact introduce a significant ( approximately 30%) level of stereoisomerism in the products by alkali-catalyzed keto-enol tautomerizations. Milder alkaline conditions were used to overcome this problem, reducing the contamination to <5%. The elimination by-products from this reaction were isolated and characterized, allowing the mechanism of alkaline degradation of hyaluronan to be investigated for the first time. beta-Glucuronidase was used to remove nonreducing-terminal glucuronic acid residues from oligosaccharides. Odd-numbered oligosaccharides with terminal glucuronic acid residues isolated from hyaluronidase digests are shown to originate from acid-catalyzed acetal hydrolysis during boiling denaturation and also have significant levels of stereochemical impurities.

Microscale preparation of even- and odd-numbered N-acetylheparosan oligosaccharides

In order to prepare a series of N-acetylheparosan (NAH)-related oligosaccharides, bacterial NAH produced in Escherichia coli strain K5 was partially depolymerized with heparitinase I into a mixture of even-numbered NAH oligosaccharides, having an unsaturated uronic acid (DeltaUA) at the non-reducing end. A mixture of odd-numbered oligosaccharides was derived by removing this DeltaUA in the aforementioned mixture by a 'trimming' reaction using mercury(II) acetate. Each oligosaccharide mixture was subjected to gel-filtration chromatography to generate a series of size-uniform NAH oligosaccharides of satisfactory purity (assessed by analytical anion-exchange HPLC), and their structures were identified by MALDITOF-MS, ESIMS, and 1H NMR analysis. As a result, a microscale preparation of a series of both even- and odd-numbered NAH oligosaccharides was achieved for the first time. The developed procedure is simple and systematic, and thus, should be valuable for providing not only research tools for heparin/heparan sulfate-specific enzymes and their binding proteins, but also precursor substrates with medical applications.

Complementary exploration of the action pattern of hyaluronate lyase from Streptococcus agalactiae using capillary electrophoresis, gel-permeation chromatography and viscosimetric measurements

Hyaluronic acid (HA) was treated with hyaluronate lyase (GBS HA lyase, E.C. 4.2.2.1, from Streptococcus agalactiae strain 4755), and the products have been analyzed by capillary electrophoresis (CE-UV and online CE-ESIMS), gel-permeation chromatography (GPC) and viscosimetric measurements. The resulting electropherograms showed that the enzyme produced a mixture of oligosaccharides with a 4,5-unsaturated uronic acid nonreducing terminus. More exhaustive degradation of HA led to increasing amounts of di-, tetra-, hexa-, octa- and decasaccharides. Using CE, linear relationships were found between peak area of the observed oligosaccharides and reaction time. Determination of viscosity at different stages of reaction yielded an initial rapid decrease following Michaelis-Menten theory. A reaction time-dependent change in the elution position of the HA peak due to partial digestion of HA with GBS hyaluronate lyase has been observed by GPC. These results indicated that the HA lyase under investigation is an eliminase that acts in a nonprocessive endolytic manner, as at all stages of digestion a mixture of oligosaccharides of different size were found. For GBS HA lyase from Streptococcus agalactiae strain 3502, previously published findings reported an action pattern that involves an initial random endolytic cleavage followed by rapid exolytic and processive release of unsaturated disaccharides. Our results suggest that differences between the two enzymes from distinct S. agalactiae strains (GBS strains 4755 and 3502) have to be considered.