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Heparin, a sulfated polysaccharide belonging to the family of glycosaminoglycans, was discovered in the beginning of the 20th century and was initially identified as a procoagulant isolated from liver tissue. After the first application in patients approximately 30 years later, further purification identified the major as well as minor, but important, component units of the complex chain mixtures constituting heparin and the multiplex actions became a scientific challenge recently. A series of "Glycosaminoglycan symposium-anticoagulant and nonanticoagulant actions" developed over the past 20 years and focused on this topic has published research data in three issues of Seminars in Thrombosis & Hemostasis and in several other international scientific journals. The latest developments on the methods of analysis, the synthesis, the degradation by heparanases and the nonanticoagulant effects in tumor growth, in anti-inflammatory diseases, and in Alzheimer diseases as presented in the 21st symposium are summarized in the present overview on the occasion of the 40th anniversary of the journal with special reference to the journal's founding Editor in Chief, Eberhard F. Mammen., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

The integrin VLA-4 is important for the metastatic dissemination of melanoma cells. We could recently show that heparin can block VLA-4 binding, which contributes, next to blocking P- and L-selectin, to the understanding of antimetastatic activities of heparin. The matricellular ligand Cyr61, secreted by numerous tumours, is responsible for increased tumourigenicity and metastasis. This has been attributed to Cyr61 binding to, and thus activating integrins. However, a VLA-4/Cyr61 axis has not yet been reported. Since Cyr61 possesses heparin binding capabilities, Cyr61 can be supposed as potential target for heparin to indirectly interfere with integrin functions. The present in vitro studies address (i) the existence of a Cyr61/VLA-4 axis and (ii) the functional relevance of heparin interference via Cyr61. The C-terminal module III of Cyr61 could be exposed as nanomolar affine binding site for VLA-4. A shRNA-based knockdown of Cyr61 in MV3 human melanoma cells reduced VLA-4-mediated cell binding to VCAM-1, migration on fibronectin, and integrin signalling functions significantly. Using a biosensor approach we provide insight into heparin interference with this process. The low-molecular-weight heparin tinzaparin, but not the pentasaccharide fondaparinux, binds module IV of Cyr61 with micromolar affinity. But tinzaparin cannot interfere with Cyr61 accumulation onto syndecan-4, indicating different Cyr61 binding sites for heparin and other GAGs. Nonetheless, tinzaparin affects the VLA-4 binding and signalling functions selectively via Cyr61 already at very low concentration most likely by blocking the cellular secreted free Cyr61. This study emphasises Cyr61 as promising, and hitherto not considered target for heparin to selectively influence integrin functions.

Hydrogen peroxide (H2O2) and Cu(OAc)2 or FeSO4 (Fenton type reagents) perform heparin (Hep) depolymerisation to low-molecular-weight heparin (LMWH) following a radical chain mechanism. Hydroxyl (OH) radicals which are initially generated from H2O2 reduction by transition metal ions abstract hydrogen atoms on the heparin chain providing carbon centred radicals whose decay leads to the depolymerisation process. The main depolymerisation mechanism involves Hep radical intermediates that cleave the glycosidic linkage at unsulphated uronic acids followed by a 6-O-nonsulphated glucosamine, thus largely preserving the pentasaccharide sequence responsible for the binding to antithrombin III (AT). Both the transition metal ions influence the overall efficiency of the radical chain processes: Fe2+ acting as a catalyst, while Cu2+ acts as a reagent. LMWHs, especially those afforded by Cu2+, are somewhat unstable to the usual basic workup. However, this lack of stability can be eliminated by a previous NaBH4 reduction. Furthermore, with Cu2+, the process is much more reproducible than with Fe2+. Therefore, for the process of Fenton type depolymerisation of heparin, the use of Cu(OAc)2 is clearly preferable to the more "classical" FeSO4. The resulting activities and characteristics of these LMWHs are peculiar to these oxidative radical processes. In addition, LMWH provided by H2O2/Cu(OAc)2 in optimised conditions was found to posses anti-Xa and anti-IIa activities comparable to those of LMWHs currently in clinical use.

As part of a more extensive investigation on structural features of different low-molecular-weight heparins (LMWHs) that can affect their biological activities, Enoxaparin, Tinzaparin and Dalteparin were characterised with regards to the distribution of different chain length oligosaccharides as determined by size-exclusion (SE) chromatography, as well as their structure as defined by 2D-NMR spectra (HSQC). The three LMWHs were also fractionated into high affinity (HA) and no affinity (NA) pools with regards to their ability to bind antithrombin (AT). The HA fractions were further subfractionated and characterised. For the parent LMWHs and selected fractions, molecular weight parameters were measured using a SE chromatographic system with a triple detector (TDA) to obtain absolute molecular weights. The SE chromatograms clearly indicate that Enoxaparin is consistently richer in shorter oligosaccharides than Tinzaparin and Dalteparin. Besides providing the content of terminal groups and individual glucosamine and uronic acid residues with different sulfate substituents, the HSQC-NMR spectra permitted us to evaluate and correlate the content of the pentasaccharide, AT-binding sequence A-G-A*-I-A (AT-bs) through quantification of signals of the disaccharide sequence G-A*. Whereas the percent content of HA species is approximately the same for the three LMWHs, substantial differences were observed for the chain distribution of AT-bs as a function of length, with the AT-bs being preferentially contained in the longest chains of each LMWH. The above information will be useful in establishing structure-activity relationships currently under way. This study is therefore critical for establishing correlations between structural features of LMWHs and their AT-mediated anticoagulant activity.

Recently, certain batches of heparin have been associated with an acute, rapid onset of serious side-effects indicative of allergic-type reactions. These reports generated significant concern regarding the possible presence of a dangerous contaminant within heparin and highlighted the need to re-assess the purity criteria of heparin preparations for clinical use. Given the nature of the array of all possible contaminants, traditional screening tests cannot safely differentiate between contaminated and uncontaminated heparin preparations. Mono- and bi-dimensional NMR spectroscopy are powerful techniques that are able to detect and quantify a wide variety of potential sulfated polysaccharide contaminants. As such, these techniques are powerful tools for the analysis and assessment of heparin preparations.

Individual low molecular weight heparins (LMWHs) exhibit distinct pharmacological and biochemical profiles because of manufacturing differences. Correlation of biological properties with particular structural motifs is a major challenge in the design of new LMWHs as well as in the development of generic versions of proprietary LMWHs. Two-dimensional nuclear magnetic resonance (NMR) spectroscopy permits identification and quantification of structural peculiarities of LMWH preparations. In this article, heteronuclear single quantum coherence spectroscopy, previously used to determine variously substituted monosaccharide components of heparan sulfate (HS) and HS-like glycosaminoglycan mimics, has been applied to the structural characterization of three commercially available LMWHs (enoxaparin, dalteparin, and tinzaparin). Relevant residues belonging to the parent heparin, as well as minor residues generated by each depolymerization procedure, have been characterized and quantified. The use of a high-sensitivity NMR spectrometer (600 MHz equipped with cryoprobe) allowed the accurate quantification of residues with sensitivity better than 1 to 2%.

A low molecular weight heparin (LMWH) obtained by a depolymerization process induced by a Fenton-type reagent was characterized in depth by nuclear magnetic resonance (NMR) spectroscopy. The depolymerization involves the cleavage of glycosidic bonds, leading to natural terminal reducing end residues, mainly represented by N-sulfated glucosamine (A (NS)). Natural uronic acids, especially the 2- O-sulfate iduronic acid (I (2S)), are also present as reducing residues. A peculiar reaction results, such as the disappearance of the nonsulfated iduronic acid residues when followed by 6-O-nonsulfated glucosamine, and the decrease of the glucuronic acid when followed by the N-acetylglucosamine, were observed. Iduronic acid residues, followed by 6- O-sulfate glucosamine (A (Nx,6S)), and the glucuronic acid residues, followed by A (NS) residues, were not modified. A few minor internal chain modifications occur, possibly arising from oxidative breaking of the bond between C2-C3 of glucosamine and uronic acids, suggested by evidence of formation of new -COR groups. Finally, no change was observed in the content of the N-sulfated, 6-O-sulfated glucosamine bearing an extra sulfate on 3-O, which is considered the marker of the active site for antithrombin. With respect to the original heparin, this LMWH is characterized by a lower number of nonsulfated uronic acid residues, and as a consequence, by a lower degree of structural heterogeneity than LMWHs prepared with other procedures.

Heparin-like polysaccharides possess the capacity to inhibit cancer cell proliferation, angiogenesis, heparanase-mediated cancer cell invasion, and cancer cell adhesion to vascular endothelia via adhesion receptors, such as selectins. The clinical applicability of the antitumor effect of such polysaccharides, however, is compromised by their anticoagulant activity. We have compared the potential of chemically O-sulfated and N,O-sulfated bacterial polysaccharide (capsular polysaccharide from E. COLI K5 [K5PS]) species to inhibit metastasis of mouse B16-BL6 melanoma cells and human MDA-MB-231 breast cancer cells in two in vivo models. We demonstrate that in both settings, O-sulfated K5PS was a potent inhibitor of metastasis. Reducing the molecular weight of the polysaccharide, however, resulted in lower antimetastatic capacity. Furthermore, we show that O-sulfated K5PS efficiently inhibited the invasion of B16-BL6 cells through Matrigel and also inhibited the in vitro activity of heparanase. Moreover, treatment with O-sulfated K5PS lowered the ability of B16-BL6 cells to adhere to endothelial cells, intercellular adhesion molecule-1, and P-selectin, but not to E-selectin. Importantly, O-sulfated K5PSs were largely devoid of anticoagulant activity. These findings indicate that O-sulfated K5PS polysaccharide should be considered as a potential antimetastatic agent.

Heparanase is an endo-beta-D-glucuronidase that cleaves the heparan sulfate chains of heparan sulfate proteoglycans and is implicated in angiogenesis and metastasis. With the aim of establishing a simple and reliable method for studying the susceptibility of heparin/heparan sulfate oligosaccharides to be cleaved by heparanase, an on-line ion pair reversed-phase high-performance liquid chromatographic/electrospray ionization mass spectrometric method was set up. The method works in the micromolar range of concentration and does not require derivatization of the substrate or of the products. It is based on mass identification of oligosaccharide fragments generated by heparanase and their quantification with reference to an internal heparin disaccharide standard. Substrates were (1) the synthetic pentasaccharides GlcN (NS,6S) - GlcA - GlcN (NS,3S,6S) - IdoA (2S) - GlcN (NS,6S) - OMe (AGA*IA (M)) and GlcN (NS,6S) - GlcA - GlcN (NS,6S) - IdoA (2S) - GlcN (NS,6S) - OMe (AGAIA (M)), corresponding to the heparin/heparan sulfate active site for antithrombin, and to the same sequence devoid of the 3- O-sulfate group in the central glucosamine, respectively; and (2) two natural heparin octasaccharides containing the AGA*IA sequence in different locations along the chain. The two pentasaccharides exhibited a higher susceptibility to heparanase cleavage with respect to the octasaccharides. The commercial availability of AGA*IA (M) makes it an ideal substrate to determine the specific activity of heparanase preparations. The present method could also be used for rapid screening of potential heparanase inhibitors.

Heparin, a natural glycosaminoglycan (GAG), is widely used for the treatment of thrombotic diseases. Most of its side effects are related to its ability to bind to different proteins, thus interfering with its target biological activity. To gain insight into structure-activity relationships, we investigated the interaction of a homogeneous series of sulfated polysaccharides, derived from controlled desulfation of a supersulfated low-molecular-weight heparin (LMWH) with the target enzymes human antithrombin (AT) and thrombin (T). In addition, we analyzed the activation process of the serpin AT against T and factor Xa (FXa). A nonlinear correlation between the strength of the AT-heparin complex and the polysaccharide sulfation degree was observed, whereas only a modest modulation of T binding to heparin occurred. The efficiency of the LMWH derivatives in activating AT toward the proteases was generally high for derivatives exhibiting a low dissociation constant. Only the supersulfated heparin showed a serpin activation ability higher than expected from the affinity studies. Examination of the sulfation pattern in the light of the above results suggests a key role of the substitution of the iduronic acid residue in the heparin-mediated serpin binding and activation processes. Indeed, sulfation at position 2 of the uronic acid is beneficial, whereas 2,3-disubstitution generates unfavorable contacts between the GAG and AT. Glucosamine sulfation at position 6 appears to grant increased catalytic efficiency. These results indicate that chemical modification of the heparin sulfation pattern can be used to modulate binding specificity and activity toward its biological targets.

A homogeneous set of low-molecular weight heparins, chemically modified to yield different degrees of sulfation, were investigated for their ability to interfere with the antithrombin (AT)-factor Xa (FXa) interaction process in the presence or absence of physiological concentrations of calcium ions. The heparin-AT dissociation constants were not appreciably affected by the presence of the metal ion, whereas the catalytic process was strongly dependent on Ca 2+. Our data suggest that AT binding to heparin represents the main factor driving the FXa inhibition process. In addition, the presence of the metal ion is likely to mask favorable AT- heparin ionic contacts occurring with the highly sulfated material. These results help in assessing proper structure-activity relationships for glycosaminoglycans, a multitarget family of biologically active compounds.

Sulfated glycosaminoglycans (GAGs) are amenable to a number of chemical modifications that modulate their biological activity. N-sulfate groups can be exposed and N-acylated (usually N-acetylated), specific O-sulfate groups can be removed, and free hydroxyl groups (either preexisting in the original GAG or exposed by desulfation) can be sulfated. Heparin/heparan sulfate, chondroitin sulfate, and dermatan sulfate have been variously desulfated or sulfated to afford novel GAGs with protein binding and associated biological properties different from those of the original GAGs. Regiospecific sulfation of N-acetyl heparosan ( E. coli K5 polysaccharide) afforded a number of derivatives, some endowed with antithrombotic activity and others with antimetastatic properties. Most of the activities could be correlated with typical sulfation patterns along each GAG backbone. Glycol splitting of nonsulfated glucuronic residues (including a critical residue in the pentasaccharide sequence of the active site for antithrombin) leads to substantial loss of anticoagulant activity of heparin. Partial removal of sulfate groups at position 2 of iduronic acid residues followed by glycol splitting of all nonsulfated uronic acid residues afforded nonanticoagulant, antiangiogenic heparins.

To improve the understanding of the biological functions and pharmacology of heparin and dermatan sulfate, low-molecular-weight heparin (LMWH) and low-molecular-weight dermatan sulfate (LMWDS) were labeled with tyramine (T) by covalently linking T to the terminal residue of 2,5-anhydromannose (or 2,5-anhydrotalose for dermatan sulfate). The covalent labeling was demonstrated by nuclear magnetic resonance spectroscopy. The tyramine-labeled LMWH (LMWH-T) was also labeled with fluorescein (F) by further reacting it with fluorescein isothiocyanate. The fluoresceinated LMWH-T (LMWH-T,F ) was used to analyze biological functions on blood coagulation and binding to leukocytes. The biological activities on factor Xa and thrombin inhibition remained unchanged compared with the parent compound. Flow cytometric analysis of leukocytes demonstrated binding of the modified heparin to granulocytes, monocytes, and lymphocytes, the half-live being twice as long as the antifactor Xa activity. F-labeled heparin was displaced by unlabeled heparin from all three populations of leukocytes. Binding of heparin to leukocytes may play an important role in inflammation and atherosclerosis.

Binding to proteins usually induces perturbation of nuclear magnetic resonances of ligand molecules. Using sensitive nuclear magnetic resonance (NMR) spectroscopy techniques, these perturbations have been measured for heparin oligosaccharides in aqueous solution in the presence of proteins and the NMR data have been used to characterize the three-dimensional (3D) structure of the oligosaccharides in the bound state. The pentasaccharide corresponding to the active site of heparin/heparan sulfate for antithrombin (AT) adopts in the complex with the protein a conformation different from that in the absence of the protein. A notable difference involves the 2-O-sulfated iduronic acid (IdoA2S) residue, which is driven to adopt an exclusively skew-boat @affil2: 2S 0 form in the complex. In addition, complexing induces a change in the geometry around the glycosidic linkage between the nonreducing end glucosamine and the adjacent glucuronic acid residue as compared with the free state. NMR and molecular modeling data also indicate that the 2-O-sulfate group in the IdoA2S residue is not directly involved in binding to AT. This suggests that its role is mainly that of affecting the conformational equilibrium of this residue, leading to a 3D structure of pentasaccharide in the bound state that meets the stereochemical requirements of the receptor and results in high-affinity binding to the protein. On the other hand, NMR studies of heparin tetrasaccharides in the presence of fibroblast growth factors FGF-1 and FGF-2 indicate that FGF binding stabilizes the @affil1: 1C 4 conformation of the IdoA2S residue directly involved in binding. These studies also confirm the crucial role of the 6-O-sulfate group on at least one glucosamine residue in the formation of the complex with FGF-1 but not with FGF-2.

Most of the biological effects of heparin and low molecular weight (LMW) heparins are related to their ability to bind to many different proteins. To gain insight into structure-activity relationships, we investigated quantitatively the interactions of a series of sulfated LMW heparins of similar molecular weights (derived from statistical desulfation of a supersulfated heparin) with the target enzymes human antithrombin (AT) and thrombin (T). In addition, we analyzed the activation of the protease inhibitor against T and factor Xa (FXa). A nonlinear correlation between the strength of the AT-heparin complex and the degree of sulfation of the LMW heparins was observed, whereas only a modest modulation of T binding to heparin occurred. The efficiency of the heparin derivatives in activating AT toward the proteases is generally high for derivatives exhibiting a low dissociation constant. Only the supersulfated LMW heparin showed serpin activation ability higher than expected from the affinity studies. These results indicate that chemical modification of the sulfation pattern of LMW heparin can be used to efficiently modulate binding affinity and activity toward biological targets.

A process to generate glycosaminoglycans with heparin- and heparan sulfate-like sequences from the Escherichia coli K5 capsular polysaccharide is described. This polymer has the same structure as N-acetylheparosan, the precursor in heparin/ heparan sulfate biosynthesis. The process involves chemical N-deacetylation and N-sulfation, enzymatic conversion of up to 60% of the D-glucuronic acid to L-iduronic acid residues, and chemical O-sulfation. Because direct sulfation afforded unwanted 3-O-sulfated (instead of 2-O-sulfated) iduronic acid residues, a strategy involving graded solvolytic desulfation of chemically oversulfated C5-epimerized sulfaminoheparosans was assessed using persulfated heparin and heparan sulfate as model compounds. The O-desulfation process was shown to increase the anti-factor Xa activity of oversulfated heparin.

Matrix-Assisted Laser Desorption Ionization (MALDI) mass spectrometry (MS) has emerged as a powerful, sensitive technique for structural analysis of glycosaminoglycans (GAGs) and their fractions and fragments. Whereas the molecular size of low sulfated or nonsulfated species (such as low-molecular weight [LMW] K5 polysaccharides) can be directly determined up to molecular weights (MWs) of 12 kD, polysulfated species require complexing with a basic polypeptide and at present can be characterized (in terms of both MW and end residues) up to the size of a decasaccharide, even in complex mixtures. MALDI spectra of GAG oligosaccharides in the presence of a complexing protein permit to assess binding to the protein and the presence of multimeric complexes.

The sulfation patterns of pig and bovine mucosal commercial heparin preparations can be characterized and distinguished from each other easily by analysis of their monodimensional proton and carbon nuclear magnetic resonance ((1)H and (13)C-NMR) spectra. NMR spectroscopy can detect and quantify signals associated with major sequences as well as with minor residues such as the typical ones associated with the antithrombin (AT) binding sequence and the "linkage region." Contaminants arising from industrial preparation processes are also detectable.

Low molecular weight heparins (LMWHs) obtained by different depolymerization processes can be distinguished from each other by characteristic end-residues, which are easily identified and quantified by nuclear-magnetic-resonance (NMR) spectroscopy. NMR spectroscopy characterizes major sulfation patterns as well as minor sequences such as the antithrombin-binding sequence and the linkage region of LMWHs. Artifacts associated with base-induced modifications such as the formation of iduronic acid epoxide and aziridine derivatives of N-sulfoglucosamine residues can also be detected. The influence of these modifications on the binding of heparins and LMWHs to proteins other than antithrombin are discussed.

Dermatan sulfate (DS) is a component of connective tissue and catalyzes the heparin cofactor II-mediated inhibition of thrombin. Low-molecular-mass dermatan sulfates (LMMDS) are produced to prolong the antithrombotic activity of this substance. Cleavage of DS by nitrous acid leads to an LMMDS with a terminal 2,5-anhydrotalose (At) group at the reducing end which can react with primary amines. Tyramine (Tyr) was bound to the terminal At of LMMDS using reductive amination. LMMDS-tyr is produced using DS. LMMDS desacetglated were produced using totally deaminated DS. These compounds were employed as a model for the characterization of DS using NMR spectroscopy. The purity of the compounds was checked using capillary electrophoresis. The structure of the products was proven by 1H- and 13C-NMR spectroscopy. LMMDS-Tyr was radiolabeled with 125I for use in a radioimmunoassay. The anti-Xa activity and antithrombin activity of the tyramine-labeled DS are very low. The clotting assays Heptest, aPTT, thrombin time, and ecarin time indicate a highly anticoagulant-active substance. The heparin cofactor II-mediated inhibition of thrombin is similar to the parent compound. LMMDS were labeled "endpoint-attached." They are a new tool to understand the actions of DS in biologic systems.

Low molecular weight heparins (LMWHs) are considered to be the agent of choice for the prophylaxis of DVT in medical and surgical patients. Conventionally, these agents have been produced by fractionation of or by chemical or enzymatic depolymerization of native heparin. The fractionated heparin retains many of its biological properties such as AT III affinity and sulfate content gamma-irradiation (60Co) has been used to depolymerize GAGs (De Ambrosi et al. In: biomedical and Biotechnological Advances in Industrial Polysaccharides, pp. 45-53). This procedures has now been used for the preparation of LMWH derivatives of varying molecular weight. The current studies examine the biochemical and pharmacologic profile of one such gamma-irradiated depolymerized heparin. In standard clotting and amidolytic antiprotease assays (PT, APTT, AXa, Alla), gamma-irradiated depolymerized heparin produced equal or stronger activity when compared to a LMWH produced by nitrous acid depolymerization and retained the ability to active AT III and HCHII. Initial results indicate that LMWHs produced by gamma-irradiation exhibit comparable antithrombotic actions to those produced by chemical depolymerization when measured in animal models of thrombosis. gamma-Irradiation may be a useful method for the production of LMWHs.

Unfractionated heparin and LMMH were substituted with different lipophilic organic compounds. Specifically endpoint attached (LMMH-tyramine and LMMH-tyramine-FITC) and nonspecifically substituted heparins (acylated heparins, and LMMH-biotin and LMMH-cholesterol hemisuccinate) were obtained. The lipophilically substituted heparins were analysed by HPSEC and showed different retention times, high peak purity, different UV/VIS absorbances, and areas under the absorbance time curve. The determination of the average molecular mass Mn, Mm, and Mz and the polydispersity P was performed by PAGE. The substituted heparins showed an increase in their molecular mass Mm, ranging from 2.9 to 129.7% unfractionated heparin and 3.9 to 224.0% (LMMH) compared with the parent compounds (unfractionated heparin and LMMH). The anticoagulant activity was measured by anti-Factor Xa. Lipophilically modified heparin had an aXa activity ranging from 52 to 168 U/mg (unfractionated) and 60 to 108 U/mg (LMMH) and antithrombin activity ranging from 31 to 270 U/mg (unfractionated) and 5 to 15 U/mg (LMMH). The thrombin generation inhibition assay demonstrated an effective anticoagulant potency of the modified compounds. They were neutralized by different amounts (1.1 to 4.1, w/w) of protamin. 1H NMR spectroscopy revealed the specific endpoint attachment of tyramine to LMMH and FITC to LMMH-tyramine. The lipophilically modified heparins showed intact anticoagulant properties and are now used for pharmacokinetic investigations.

Heparin, NAcHep, DS, and CS were labeled with deuterium by N-reacetylating, with the deuterated acetic anhydride (CD3CO)2O, GAGs previously N-deacetylated (by hydrazinolysis) to the desired extent. Degrees of deuteration of the present preparations, as determined by 2H- and 1H-NMR were 15%, 51%, 49%, and 79% for heparin, NAcHep, DS, and CS, respectively. The NMR analysis (including the 13C spectra) of the labeled products indicated that deuterium labeling did not involve any substantial modification of the GAG structures. Also NMR signals associated with specific sequences of heparin for antithrombin and of DS for heparin cofactor II were essentially the same in the unlabeled and in the deuterated GAGs. The substantial retention of the original structure was confirmed by data on the degree of sulfation (by conductimetry) and on the electrophoretic mobility in acid buffer. On the other hand, HPLC/SEC data indicated some depolymerization of heparin and DS in the N-deacetylation step of the labeling reactions. HPLC/MS spectrometry permitted a clear identification of disaccharide and tetrasaccharide fragments obtained from deuterated GAGs by enzymic (heparinase, chondroitinase ABC) or chemical depolymerization (deaminative cleavage, Smith degradation), opening new prospects for studies of human pharmacokinetics, with differentiation of exogenous from endogenous GAGs.