NEW PATHWAY OF HEPARAN-SULFATE DEGRADATION IDURONATE SULFATASE AND N-SULPHOGLUCOSAMINE 6-SULFATASE ACT ON THE POLYMER-CHAIN PRIOR TO DEPOLYMERIZATION BY A N-SULFO-GLUCOSAMINIDASE AND GLYCURONIDASES IN THE MOLLUSK TAGELUS-GIBBUS

It has previously been shown that in the mollusc Anomalocardia brasili ana the desulphation of chondroitin sulphate precedes its depolymerisa tion by beta-glucuronidase and beta-N-acetylgalactosaminidase (Sousa J r. et al. J. Biol. Chem. 1990;265:20150-20155). This led us to investi gate whether in molluscs, sulphatases also act on heparan sulphate bef ore its depolymerisation by glycosidases. Radioactively labelled [S-35 ]heparan sulphate was extensively degraded by enzyme extracts prepared from the mollusc Tagelus gibbus. Several enzymes acting in concert de grade the compound to inorganic sulphate, glucosamine N-sulphate, N-ac etylglucosamine-6 sulphate and other oligosaccharide products. These r esults indicate the presence of iduronate sulphatase, N-sulphoglucosam ine 6-sulphatase alpha-N-sulphoglucosaminidase, beta-glucuronidase and alpha-L-iduronidase. The di- and mono-saccharide composition of the o ligosaccharides were analysed with the aid of heparitinase II from Fla vobacterium, heparimum. These analyses led to the characterisation of two sulphatases that act on the polymer chain removing sulphates from the C-2 position of iduronic acid residues and the C-6 position of the glucosamine moieties, respectively. The different enzymes were partia lly fractionated by ion exchange chromatography and molecular sieving. These results led to the proposition of a new pathway of degradation of heparan sulphate where sulphatases act directly on the polymer chai n which is then depolymerised by several glycosidases. (C) 1998 Elsevi er Science Inc. All rights reserved.