Figure 1

Biosynthesis of GSL core structures. GSL biosynthesis is initiated by the transfer of Glc to ceramide (Cer) catalyzed by the Ugcg enzyme. After addition of β1,4-linked Gal by Lac-Cer synthase, distinct core structures are defined by the action of different glycosyltransferases. The B3gnt5 enzyme catalyzes the Lc3 structure, which is the core of lactoseries GSL. The elongation of Lc3 by a α1,3-fucosyltransferase and a β1,4-galactosyltransferase yields the SSEA-1 antigen. ●, Glc; ○, Gal; ■, GlcNAc; ◆ Sia; ▲, Fuc.