Dermatan hydrolysis

Dermatan sulfate, also termed chondroitin sulfate B, a related glycosaminoglycan constituent of connective tissue, was known to be composed of galactosamine and a uronic acid, originally believed to be glucuronic acid but then claimed to be iduronic acid based largely on color reactions and paper chromatography. However, the d or L-enantiomer status of the latter monosaccharide was not clear. Jeanloz and Stoffyn unequivocally characterized the monosaccharide as L-iduronic acid by consecutive desulfation, reduction, and hydrolysis of the polysaccharide, followed by isolation of the crystalline 2,3,4-tri-0-acetyl-l,6-anhydro-/ -L-idopyranose, which was shown to be identical to an authentic specimen synthesized from 1,2-0-isopropylidene-/ -L-idofuranose.34... 

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 3.2.1.76] catalyzes the hydrolysis of a-L-iduronosidic linkages in desuffated dermatan. 

Aldurazyme polymorphic variation of human a-L-iduronidase lysosomal hydrolase hydrolysis of terminal a-L-iduronic acid residues of dermatan sulfate and heparin sulfate No genotoxicity studies clinical trials Studies to assess mutagenic and carcinogenic potential have not been conducted No warnings or precautions regarding carcinogenic risk... 

Chondroitin 4- and 6-sulfates were originally designated as chondroitin sulfate A and C, respectively, and the close similarity in structure between them is demonstrated by the fact that both mucopolysaccharides yield the same disaccharide (chondrosine) on controlled, acidic hydrolysis together with sulfuric and acetic acids. Chondroitin 4-sulfate or chondroitin 6-sulfate, or both, occur in cartilage and adult bone, and the former mucopolysaccharide is a minor constituent of ligamentum nuchae and cornea (M17). Chondroitin 6-sulfate is a minor constituent of umbilical cord and occurs with dermatan sulfate (chondroitin sulfate B) and hyaluronic acid in heart valves and adult connective tissue (M17). An acid mucopolysaccharide isolated from human plasma resembles chondroitin 4-sulfate in its properties (S4). 

Acidic hydrolysis of dermatan sulfate yielded D-galactosamine, acetic acid, sulfuric acid, and a uronic acid with chromatographic properties indistinguishable from those of L-iduronic acid (H12). The first crystalline derivatives of the uronic acid component of dermatan sulfate were obtained by Jeanloz and Stoffyn (J4, S19) and permit an unequivocal... 

Proteoglycans undergo continuous turnover at rates dependent upon the nature of the proteoglycan and tissue location. Their half-life is between one and several days. Degradation of proteoglycans is initiated by proteolytic enzymes that release glycosaminoglycans the latter are subsequently degraded by lysosomal enzymes. Some of the products of hydrolysis (e.g., dermatan sulfate and heparan sulfate) are excreted in the urine. 

Various dermatan sulfate derived di-, tetra-, hexa-, octa-, deca- and dodeca-saccharide mixtures have been prepared and purified (on a semi-preparative scale) by controlled depolymerization of dermatan sulfate using chondroitin ABC lyase, The pathways of InsPe hydrolysis by phytase from wheat bran of Triticum aestivum have recently been established. ... 

Disaccharides from glycosanunoglycans. - Unsaturated disaccharides released by enzymic hydrolysis of chondroitin sulphate have been separated on a primary amino-containing gel column, those from hyaluronic acid, chondroitin sulphate and dermatan sulphate by reversed-phase h.p.l.c. on an amido-phase as their dansyl hydrazone derivatives with chemiluminescence detection," and those from dermatan sulphate and heparin by ion-pair reversed-phase microbore h.p.Lc. coupled with ion-spray m.s. for use in monitoring their presence in patients treated vrith these polysaccharides intravenously. ... 

A dodecasaccharide that was obtained by hydrolysis of dermatan sulphate with testicular hyaluronidase, chondroitin lyase AC, and jS-D-glucuronidase yielded a sulphated 2-amino-2-deoxy-D-galactose derivative when treated with human serum at pH 4.5 or 7.0. No further degradation of the substrate occurred, suggesting that normal human serum possesses an cxo-jS-D-acetamidodeoxyhexosidase that is active towards dermatan sulphate. 

Values for Km and have been determined for the degradation of chondroitin 4- and 6-sulphates, chondroitin 4-sulphate proteoglycan, dermatan sulphate, and hyaluronic acid by a chondroitin sulphate lyase ABC obtained from Proteus vulgaris. The hydrolysis of chondroitin 4-sulphate by the enzyme was inhibited by hyaluronic acid, but not by keratan sulphate. The findings were discussed in connection with the use of chondroitin sulphate lyase ABC as a reagent for the degradation of tissue glycosaminoglycans. 

The presence of both glucuronic add and a-linkages in heparin and heparitan sulfate results in a polysaccharide resistant to hydrolysis, and the uronic acid part is decarboxylated before the amino sugar part is completely released. Similar difficulties are encountered in the hydrolysis of chondroitin 4- and 6-sulfates (chondroitin sulfates A and C), whereas dermatan sulfate ()8-heparin, chondroitin sulfate B) can be hydrolyzed under conditions mild enough to allow the isolation of iduronic add. 

Hydrolysis of dermatan sulfate with strong mineral acid afforded equal molecular amounts of acetic acid, sulfuric acid and D-galactosamine. In contrast to the molecule of chondroitin sulfate, the molecule of dermatan sulfate is far more susceptible to hydrolysis, and treatment with dilute acid did not afford a disaccharide, but an undegraded uronic add. Paper chromatographic analysis indicated that it was similar to iduronic acid , which explains the low intensity of the color shown by dermatan sulfate in the carbazole reaction. 

Reduction of methylated desulfated dermatan sulfate with sodium boro-hydride transformed the L-iduronic acid moiety into an L-idose moiety. Hydrolysis, followed by adsorption of the hexosamine fraction, gave a neutral fraction consisting of sirupy i,6-anhydro-2,3-di-0-methyl-/ -L-ido-pyranose (XXIX), identical with a synthetic sample, and of a mixture of 2,3-di-O-methyl, 2-0-methyl and 3-O-methyl-D-glucose. The yield of XXIX was low, because of the volatility of the substance, which was further characterized as a crystalline mono- -azobenzoate. No other methylidoses were observed . 

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