| 摘要 |
A single vessel cyclic synthesis process for preparation of a sialyl alpha 2}3 beta galactoside is disclosed. In accordance with this process, a sialyltransferase acceptor is sialylated in an aqueous reaction medium by an alpha (2,3)sialyl transferase and CMP-sialic acid to form a sialyl donor substrate and CMP. In the presence of the trans-sialidase of Trypanosoma crusi, that sialyl donor substrate provides a sialyl group for a transsialidase acceptor, thereby preparing the sialyl alpha 2}3 beta galactoside. The alpha (2,3)sialyltransferase acceptor is reformed upon trans-sialidation of the latter acceptor, and the sialyl donor substrate is reformed using the alpha (2,3)sialyltransferase and a CMP-sialic acid recycling system that combines CMP with sialic acid that is also present in the vessel. The Km/Vmax value for the alpha (2,3)sialyltransferase acceptor is less than one-tenth the value of Km/Vmax of the transsialidase acceptor for the alpha (2,3)sialyltransferase. |
