STRUCTURAL CHARACTERIZATION OF THE MALTOSE ACCEPTOR-PRODUCTS SYNTHESIZED BY LEUCONOSTOC-MESENTEROIDES NRRL B-1299 DEXTRANSUCRASE

The glucooligosaccharides (GOS), produced by Leuconostoc mesenteroides NRRL B-1299 dextransucrase through an acceptor reaction with maltose and sucrose, were purified by reverse phase chromatography. Logarithmi c plots of retention time vs. dp of the GOS gave three parallel lines suggesting the existence of at least three families of homologous mole cules. The structure (C-13 and H-1 NMR spectroscopy) and reactivity of the purified molecules of the three families were investigated. All t he products bear a maltose residue at the reducing end. The GOS in the first family (named OD) contained additional glucosyl residues all al pha-(1-->6) linked. The smallest molecule in this first series was pan ose or alpha-D-glucopyranosyl-(1-->6)-D-maltose (dp 3). All the OD mol ecules were shown to be good accepters for dextransucrase in the prese nce of sucrose. The second family, named R, was composed of linear GOS containing alpha-(1-->6)-linked glucosyl residues and a terminal alph a-(1-->2)-linked residue at the non-reducing end of the molecule; the smallest molecule in this family was alpha-D-glucopyranosyl-(1-->2)-D- panose (dp 4). The third family, R', was formed of GOS containing addi tional residues linked through alpha-(1-->6) linkages that constitute the linear chain, and an alpha-(1-->2)-branched residue located on the penultimate element of the chain, near the non-reducing end. The smal lest molecule in this series is -(1-->2)]-alpha-D-glucopyranosyl-(1--> 6)-D-panose, dp 6, R and R' GOS are very poor accepters for L. mesente roides NRRL B-1299 dextransucrase. This study makes it possible to sug gest a rather simple reaction scheme, where molecules R-i, R'(i) and O Di of the same dp all result from the glucosylation of the same GOS: O Di-l (C) 1998 Elsevier Science Ltd.