Proteoglycans and Glycoproteins from Bovine Heart Valve

Abstract

The density-gradient centrifugal and gel chromatographic behavior of the components (pro teoglycans, glycoprotein, and hyaluronic acid) of a proteoglycan fraction (U-III_a) isolated by DEAE-cellulose chromatography of a urea-containing solution of collagenase-indigestible material of bovine heart valves was examined to investigate the nature of the interactions of the components in U-III_a in more detail. A glycoprotein (buoyant density, about 1.32 g/ml) in U-III_a was separated from proteoglycans and hyaluronic acid by CsCl density-gradient (initial density 1.35 g/ml) centrifugation in the presence of 4 M guanidinium chloride. Observations under various density gradient conditions suggest that this glycoprotein in U-III_a dose not interact with proteoglycans under associative conditions. A glycoprotein (U-II) which was free from proteoglycans and contained about 2% hydroxyproline was isolated by DEAE-cellulose chromatography. U-II had a buoyant density of about 1.32 g/ml and its amino acid composition was very similar to that reported in the literature for “structural glycoprotein.” Chromatography of U-III_a on Sepharose 4B under associative solvent conditions, together with the electrophoretic patterns of the resulting fractions, indicated that almost all the proteochondroitin sulfate and proteodermatan sulfate, and a small amount of hyaluronic acid were retained within the column, while a glycoprotein was eluted near the end of the total volume. The present experiments indicate that heart valve proteoglycans from the collagenaseindigestible materials of bovine heart valves are not in the form of cartilage-type proteoglycan super-aggregates.