Degradation of heparin in mouse mastocytoma tissue

Abstract

1. Heparin was prepared from mouse mastocytoma tissue by mild procedures, including extraction of mast-cell granules with 2m-potassium chloride, precipitation of the extracted polysaccharide with cetylpyridinium chloride from 0.8m-potassium chloride and finally digestion of the isolated material with testicular hyaluronidase. The resulting product (fraction GEH) represented approx. 40% of the total heparin content of the tissue. 2. Fraction GEH was fractionated by gel chromatography on Sepharose 4B into three subfractions, with average molecular weights (¯Mw) of approx. 60000–70000 (highly polydisperse material), 26000 and 9000 respectively. Treatment of each of the subfractions with alkali or with papain did not affect their behaviour on gel chromatography. Amino acid and neutral sugar analyses indicated that the two low-molecular-weight fractions consisted largely of single polysaccharide chains lacking the carbohydrate–protein linkage region. It was suggested that these heparin molecules had been degraded by an endopolysaccharidase. 3. Pulse labelling in vivo of mastocytoma heparin with [35S]sulphate showed initial labelling of large molecules followed by a progressive shift of radioactivity toward fractions of lower molecular weight. Further, heparin-depolymerizing activity was demonstrated by incubating 35S-labelled heparin in vitro with a mastocytoma 10000g-supernatant fraction. Appreciable degradation of the polysaccharide occurred, as demonstrated by gel chromatography. In contrast, no depolymerization was observed on subjecting 14C-labelled chondroitin sulphate to the same procedure.