Heparin hydrolysis

The identification of L-iduronic acid as the major glycuronic acid constituent of heparin proved to be a much slower process than the identification of the amino sugar residue. Although this compound was detected in acid hydrolyzates of heparin116117 and heparin oligosaccharides,118 its yield was usually poor, because of the drastic conditions used for the acid hydrolysis (which are known to lead to extensive destruction of uronic acid).119120 Also, L-iduronic acid escaped detection as L-idose in the hydrolyzates of carboxyl-reduced heparin, probably because L-idose is readily converted into 1,6-anhydro-L-idose under the usual hydrolytic conditions. 

Examination of early -n.m.r. spectra of heparin and of chemically modified heparins121 prompted a reinvestigation of N,0-desulfated, carboxyl-reduced heparin, leading to the isolation of substantial amounts of L-iditol pentaacetate.121,122 In addition, improved conditions for the acid hydrolysis of heparin and carboxyl-reduced heparin gave increased recoveries of L-iduronic acid and 1,6-anhydro-L-idose, respectively.123 These findings confirmed the L-enantiomeric designation of the iduronic acid, and established that it is the main uronic acid in heparin. 

Both positional linkages (uronic acid to hexosamine and hexosamine to uronic acid) were established as being (1 — 4) by structural analysis of the previously mentioned (see Section IV), crystalline disaccharides containing D-glucuronic acid, isolated from an acid hydrolyzate of carboxyl-reduced heparin.128-129 Further evidence was obtained from the structure of the D-glucuronic acid-containing counterpart of disaccharides 6 and 8, obtained as minor products from pig-mucosal heparin following nitrous acid deamination,1110 136-138 and acid hydrolysis followed by N-acetylation,130 respectively. 

Although the glycosidic bonds of uronic acid residues are usually more resistant to acid hydrolysis than those of neutral polysaccharides,218 these linkages in heparin are more readily cleavable then those between the hexosamine and the uronic acid residues. Disaccharides obtained by exhaustive hydrolysis of heparin with 0.5 MHC1 at 80° contained hexu-... 

Some active materials are carriers for drugs (drug delivery systems), some have immobilized peptides to enable cell adhesion or migration, some are degradable by hydrolysis or by specific enzyme action. Some contain bioactive agents (e.g., heparin, thrombomodulin) to prevent coagulation or platelet activation while others incorporate bioactive groups to enhance osteo-conduction. Many include polyethylene oxide to retard protein adsorption and this is perhaps the closest we have come to a kind of inertness. 

Aldurazyme (tradename, also known as laronidase) is a recombinant version of one polymorphic variant of the human enzyme a-L-iduronidase. It was approved for general medical use in the USA in 2003 and is indicated for the treatment of patients with certain forms of the rare inherited disease MPS I. MPS I is caused by a deficiency of a lysosomal a-L-iduronidase, which normally catalyses the hydrolysis of terminal a-L-iduronic acid residues from the glycosaminoglycans dermatan sulfate and heparin sulfate. The deficiency results in accumulation of the glycosaminoglycans throughout the body, causing widespread cell and tissue dysfunction. 

This enzyme [EC 3.1.6.18], also known as glucuronate-2-sulfatase and chondro-2-sulfatase, catalyzes the hydrolysis of the 2-sulfate groups of the 2-O-sulfo-D-glucuro-nate residues of chondroitin sulfate, heparin, and hepari-tin sulfate. The enzyme does not act on iduronate 2-sulfate residues. 

Trifluoroacetic acid is volatile, and thus readily removed. This acid was used by Albersheim and coworkers for the hydrolysis of plant cell-walls,39 and has since been employed for cell walls,40-43 plant mucilages,44 blood-group oligosaccharides,45 peptidogalactoman-nans,46 heparin,47 and disaccharides in blood and urine.48,49 It has also been suggested as an alternative to 6 M hydrochloric acid in the determination of amino sugars,50 and for the hydrolysis of polyalcohols produced by periodate oxidation of polysaccharides.503 Lee... 

These are prepared by enzymatic or chemical hydrolysis of conventional heparin, their molecular weight varies from 3,000 to 7,000. They are absorbed more completely than the conventional heparin preparation and having longer duration of action. 

Synthetic heparinoid polymers such as polyanionic polyesters containing sulfamate and carboxylate groups were synthesized by hydrolysis of p(N chloro-sulfonyl beta lactam) [475]. These materials possess anti-coagulant activity (although lower than heparin) presumably due to the similarity of functional groups of this material and those found in heparin. 

After hydrolysis of carboxyl-reduced and partially desulfated heparin with hydrochloric acid, Wolfrom and coworkers117 isolated a disaccharide that was identified118 as 2-amino-2-deoxy-4-0-a-D-glucopyran-osyl-D-glucopyranose ( maltosamine ) hydrochloride, which gave a crystalline N-acetyl derivative (50). This structure was subsequently... 

Wolfrom and Rice hydrolyzed heparin in the presence of bromine in order to convert the uronic acids released into aldaric acids.24 The same method, oxidative hydrolysis, was used by Rees and coworkers in order to protect liberated 3,6-anhydrohexose residues. The... 

Fig. 8. Kinetics of unstabilized fibrin hydrolysis with complexes of immobilized heparin with fibrinogen (1), thrombin (2), fibrinolysin (plasmin) (3), and serum albumin (4),06)...

The hydrolysis of fibrinogen absorbed by immobilized heparin accounts for the decreased platelet adhesion onto modified polymers derived from HCP by additional immobilization of trypsin (see Table 18). 

Heparosine. A sulfated disaccharide has been isolated308 by partial, acidic hydrolysis of heparin, and it has been formulated as 4-0-(2-amino-2-deoxy-a-v-glucopyranosyl 6-sulfate)-D-glucuronic acid. Heparosine and its W-acetyl amide are amorphous. An amorphous disaccharide prepared by a similar procedure, was, however, believed309 to be a 2-amino-2-deoxy-(D-glucosyluronic acid)-D-glucose. 

Sundheim, G., Bengtsson-Olivecrona, G. 1987d. Hydrolysis of bovine and caprine milk fat globules by lipoprotein lipase. Effects of heparin and of skim milk on lipase distribution and on lipolysis. J. Dairy Sci. 70, 2467-2475. 

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