Nigerooligosaccharide acceptor reaction of Streptococcus sobrinus glucosyltransferase GTF-I

Nigerose and nigerooligosaccharides served as accepters for a glucosyltrans ferase GTF-I from cariogenic Streptococcus sobrinus to give a series of hom ologous acceptor products. The soluble oligosaccharides (dp 5-9) strongly a ctivated the acceptor reaction, resulting in the accumulation of water-inso luble (1 --> 3)-alpha-D-glucan. The enzyme transferred the labeled glucosyl residue from D-[U-C-13]sucrose to the 3-hydroxyl group at the non-reducing end of the (1 --> 3)-alpha-D-oligosaccharides, as unequivocally shown by N MR C-13-C-13 coupling patterns. The values of the C-13-C-13 one-bond coupli ng constant ((1)J) are also presented for the C-1-C-6 of the C-13-labeled a lpha-(1 --> 3)-linked glucosyl residue and of the non-reducing-end residue. (C) 2000 Elsevier Science Ltd. All rights reserved.