One-pot multienzyme (OPME) chemoenzymatic synthesis of brain ganglioside glycans with human ST3GAL II expressed in E. coli.

A human sialyltransferase ST3GAL II (hST3GAL II) was successfully expressed in Escherichia coli as an active soluble fusion protein with an N-terminal maltose-binding protein (MBP) and a C-terminal hexa-histidine tag. It was used as an efficient catalyst in a one-pot multienzyme (OPME) sialylation system for high-yield production of the glycans of ganglioside GM1b and highly sialylated brain gangliosides GD1a and GT1b. Further sialylation of GM1b and GD1a glycans using a bacterial α2-8-sialyltransferase in another OPME sialylation reaction led to the formation of the glycans of GD1c and brain ganglioside GT1a, respectively. The lower reverse glycosylation activity of the recombinant hST3GAL II compared to its bacterial sialyltransferase counterpart simplifies the handling of enzymatic synthetic reactions and has an advantage for future use in automated chemoenzymatic synthetic processes.