STRUCTURE DETERMINATION OF A 2''-O-(ALPHA-D-GLUCOPYRANOSE) ISOMALTOTRIOSE BY PROTON AND C-13 NMR

The glucosyltransferases from Leuconostoc mesenteroides are known to c atalyze the transfer of the D-glucosyl group of sucrose onto sugars, c ommonly named acceptors. We investigated in the present work the trans fer of the glucose moiety of sucrose onto isomaltose acceptor catalyze d by the glucosyltransferases from Leuconostoc mesenteroides. Several oligosaccharides were produced, isolated, fractionated by HPLC and cha racterized. The primary structure of the tetrasaccharide has been dete rmined as that of 2''-O-(alpha-D-glucopyranose) isomaltotriose by n.m. r. spectroscopy, using homo- and heteronuclear, shift correlated, two dimensional and n.o.e. difference experiments. This chemical structure was corrobored by C-13 spin lattice relaxation time measurements (T1) indicating that internal units B and C are notably less flexible than A and D termini units, C being the less mobile.