The presence of mono-, di-, and tri-O-acetylated
sialic acids on human cells was demonstrated by using radiochromatographic and chemical techniques. Human
melanoma cells and fresh colon tissue were biosynthetically labeled with 6- (3H)
glucosamine. Radiolabeled
sialic acids were hydrolytically removed from cellular
glycoconjugates, purified by ion-exchange chromatography, and separated by paper chromatography on the basis of the number of O-substitutions on each sialic molecule. This analytical technique characterized radiolabeled
sialic acids that migrated with the same Rf as synthetic mono-, di-, and tri-O-acetylated 14C-labeled
sialic acids. The mono-O-acetylated
sialic acids were characterized by their sensitivity to
sodium periodate oxidation and a crude mouse liver
esterase preparation. The di- and tri-O-acetylated
sialic acids were characterized by their resistance to
sodium periodate oxidation and sensitivity to the action of crude mouse liver
esterase. Chromatographically separated di- and tri-O-acetylated
sialic acids from normal human colon tissue were characterized by their respective ion molecular weights by using fast-atom bombardment-mass spectrometry. Using these methods, we chemically characterized mono, di-, and tri-O-acetylated
sialic acids expressed on human cells. Aberrant expression of O-acetylated
sialic acids was associated with
adenocarcinoma of the colon, leading to a nearly complete loss of di- and tri-O-acetylated
sialic acids.