Nigerooligosaccharide acceptor reaction of Streptococcus sobrinus glucosyltransferase GTF-I Original Research Article

Nigerose and nigerooligosaccharides served as acceptors for a glucosyltransferase GTF-I from cariogenic Streptococcus sobrinus to give a series of homologous acceptor products. The soluble oligosaccharides (dp 5–9) strongly activated the acceptor reaction, resulting in the accumulation of water-insoluble (1→3)-α-d-glucan. The enzyme transferred the labeled glucosyl residue from d-[U-13C]sucrose to the 3-hydroxyl group at the non-reducing end of the (1→3)-α-d-oligosaccharides, as unequivocally shown by NMR 13C–13C coupling patterns. The values of the 13C–13C one-bond coupling constant (1J) are also presented for the C-1–C-6 of the 13C-labeled α-(1→3)-linked glucosyl residue and of the non-reducing-end residue.