Neuraminidase activity and cell surface sialic acid turnover in Rous sarcoma virus transformed chick embryo...

Neuraminidase activity of Rous sarcoma virus transformed chick embryo fibroblasts (RSV-CEF) was assayed using an exogenous substrate, neuraminlactitol-[3H], and endogenous, cell surface [14C]-N]-acetyl-neuraminic acid. RSV-CEF had higher neuraminidase activity toward both substrates than did chick embryo fibroblasts (CEF) or nontransformed, Rous associated virus infected CEF (RAV-CEF). The total sialic acid content of RSV-CEF was lower than CEF or RAV-CEF, and more of the total sialic acid was accessible to extracellular Clostridium perfringens neuraminidase. Activity of the enzymes synthesizing and degrading the substrate for sialyltransferase, cytidine-5'-monophosphate-N-acetyl-neuraminic acid (CMP-AcNeu) was measured in order to determine whether control of substrate levels for sialyltransferase might contribute to the decreased levels of glycoprotein bound sialic acid. No change in activity of these enzymes was found in RSV-CEF as compared to CEF or RAV-CEF.