[62] Animal sialic acid transferases (sialyl-transferases)

The assay method and properties of rat mammary, sheep submaxillary, embryonic chicken brain, and colostrum sialyl-transferases are discussed, and a multiplicity of enzymes involved in their synthesis can be predicted.

Abstract

This chapter discusses the synthesis of animal sialic acid transferases (sialyl-transferases). Sialic acids are generally found as constituents of heteropolymers, although one homopolysaccharide, colominic acid is isolated from Escherichia coli K-235. The sialic acid glycosides synthesized by mammalian tissues consist of (1) oligosaccharides such as those found in milk and colostrum, (2) glycoproteins such as those found in plasma and submaxillary secretions, and (3) glycolipids such as the gangliosides of brain. In these substances, the sialic acids are glycosidically bound to galactose, N-acetylgalactosamine, or to sialic acid residues. The large variety of sialyl-glycosides produced by vertebrate tissues, a multiplicity of enzymes involved in their synthesis can be predicted. The methods discussed in the chapter, discusses the incubation conditions used for determining the transferase activity of each preparation, the method used for determining product formation is essentially the same. The enzyme preparations are incubated with labeled CMP-sialic acid in the presence and absence of potential acceptor. The assay method and properties of rat mammary, sheep submaxillary, embryonic chicken brain, and colostrum sialyl-transferases are discussed in the chapter.