Studies on glycoconjugate metabolism in developing skeletal muscle membranes

The postnatal development of mammalian skeletal muscle is characterized by changes in the properties of several key membrane glycoprotein enzymes and receptors. In the present study, CMP-sialic acid: fetuin sialyltransferase and CMP-sialic acid: lactosylceramide sialyltransferase activity was characterized in sarcolemma and sarcoplasmic reticulum membranes isolated from neonatal (0-1 week) and adult (8 week) rabbit skeletal muscle. CMP-sialic acid: fetuin sialyltransferase decreased by a factor of 10 in sarcolemma and 6 in sarcoplasmic reticulum during development, whereas CMP-sialic acid: lactosylceramide sialyltransferase activity decreased by a factor of 6 in sarcolemma and 18 in sarcoplasmic reticulum. The Km for CMP-sialic acid using the lipid acceptor declined during the development of sarcoplasmic reticulum (neonate vs. adult: 538 vs. 33 microM), but not in sarcolemma. The carbohydrate composition of sarcolemma was changed only with respect to total sialic acid content (neonate vs. adult: 67 vs. 44 nmol/mg). Similar analysis of sarcoplasmic reticulum carbohydrates showed decreases in total sialic acid, lipid-bound sialic acid, hexosamines and hexoses. The major ganglioside was GM3 for both types of membrane. No qualitative changes were observed in ganglioside composition comparing neonatal and adult membranes.