Thin-layer chromatography (TLC), gas-liquid chromatography (GLC) and high-performance liquid chromatography (HPLC) analyses of rat alpha 1-macroglobulin (RMG) and bovine submaxillary mucin (BSM) incubated with ICV in comparison with those incubated with neuraminidase from A. ureafaciens revealed that RMG and BSM incubated with ICV have a reduced amount of Neu5,9Ac2 but an increased amount of Neu5Ac. After confirmation by using purified Neu5,9Ac2 instead of RMG and BSM, it was concluded that RDE of ICV is neuraminate O-acetylesterase (9-O-acetyl N-acetylneuraminate O-acetylhydrolase (EC 3.1.1.53) catalyzing removal of the 9-O-acetyl group from Neu5,9Ac2, not cleaving the terminal Neu5Ac from glycoconjugate [182]. RMG and BSM can potentially inhibit hemagglutination by ICV at 4oC, and their inhibitory effects were abolished by pre-incubation of RMG and BSM with ICV at 37oC [182]. This evidence suggested that Neu5,9Ac2 is a receptor of ICV on the cell surface.