Differential effect of neuraminidase on the Mg 2+-ATPase, Na +-K +-Mg 2+-ATPase and 5′-nucleotidase of isolated plasma membranes

Abstract

1.1. The total content of sialic acids of the individual protein constituents of skins and hide, viz., collagen, procollagens, elastin, albumin, globulin and mucoid were quantitatively estimated by resorcinol and thiobarbituric acid methods. Of these proteins, the sialic acid content of mucoid was found to be the highest and that of citrate-soluble procollagen the lowest.2.2. The component sialic acids of each protein were identified and quantitatively estimated by a paper-chromatographic method which was standardised. N-Acetyl-neuraminic acid in higher concentration and N-glycolylneuramini acid in lower concentration were found to occur in skin albumin, globulin or mucoid whereas only N-acetylneuraminic acid could be detected in collagen, procollagens and elastin.3.3.The sialic acids were found to be easily released from these proteins by the action of purified neuraminidase (N-acetylneuraminate glycohydrolase, EC 3.2.1.18) of Clostridium perfringens, which indicated that the sialic acids were bound terminally in O-glycosidic linkages in these proteins.4.4. The major glycosidic partner for sialic acids in collagen, albumin, globulin or mucoid was identified by estimating the component hexoses and hexosamines of the original protein as well as the sialic acid-free protein before and after periodate oxidation. It was found that the reducing group of sialic acid was joined in O-glycosidic linkages to the galactose residues in these proteins.