Glycosyltransferase complexes improve glycolipid synthesis

► GM3 synthase (GM3S) activity of CHO-K1 cells increases when transfected with GD3 synthase (GD3S). ► The products of the GM3S assay were GM3 in CHO-K1 cells but GM3, GD3 and GT3in GD3S transfected cells. ► GM3 formed in the complex GalT1/GM3S/GD3S remains bound and is converted into GD3 and GT3 by GD3S. ► GM3Sfreeof GM3 is ready for new turns of LacCer sialylation, resulting in its apparent activation.