FUNCTIONAL AND BIOSYNTHETIC ASPECTS OF SIALIC-ACID DIVERSITY

Sialic acids comprise a large family of N- and O-substituted neuramini c acid derivatives as components of glycoconjugates. N-Glycolylneurami nic acid is formed from N-acetylneuraminic acid by the action of the C MP-N-acetylneuraminic acid hydroxylase studied in various animals. O-M ethylated sialic acids originate from the action of S-adenosylmethioni ne-8-O-methyltransferase studied in starfish. Sialic acids are O-acety lated at diverse positions by the action of acetyl-CoA-4-O- and -7-O-a cetyltransferases found in various animals and, leading to the O-acety lation of sialic acid glycerol side chain, also in man. Some propertie s of these enzymes are described and biological implications discussed .