| abstract |
[Problem] Importance is known to be attributed to sugar chains having sialic acid α2,3- or α2,6-linked to a non-reducing terminal of the sugar chain, and there has been a demand for such sugar chain compounds to be produced on an industrial scale. Particularly in circumstances such as when glycoprotein drugs are produced, it is essential to mass-produce sugar chains of uniform structure while controlling the mode in which sialic acid is linked (α2,6-linking or α2,3-linking). Chemically synthesizing sugar chains having sialic acid on all the non-reducing terminals is regarded to be difficult, particularly with respect to triantennary or tetraantennary N-linked complex sugar chains, and no reports of such sugar chains being chemically synthesized have been made. Efficiently preparing such sugar chains has also presented enzymological challenges. [Solution] In the present invention, it was newly discovered that sialyltransferase has activity to decompose sialic acid in a reaction product in the presence of CMP, and it was discovered that sialic-acid-containing sugar chains can be produced efficiently by enzymatically decomposing CMP. It was also discovered that conventionally-hard-to-synthesize tetraantennary N-linked sugar chains to which four molecules of sialic acid have been added by α2,6-linking could be prepared at high yield through a one-pot synthesis in which a sugar-chain-elongation reaction is carried out using a biantennary sugar chain as a starting material, without conducting purification after the individual enzyme reactions. |