21291-36-1Relevant articles and documents
Gluco-oligomers initially formed by the reuteransucrase enzyme of Lactobacillus reuteri 121 incubated with sucrose and malto-oligosaccharides
Dobruchowska, Justyna M,Meng, Xiangfeng,Leemhuis, Hans,Gerwig, Gerrit J,Dijkhuizen, Lubbert,Kamerling, Johannis P.
, p. 1084 - 1096 (2013/08/23)
The probiotic bacterium Lactobacillus reuteri 121 produces a complex, branched (1 → 4, 1 → 6)-α-D-glucan as extracellular polysaccharide (reuteran) from sucrose (Suc), using a single glucansucrase/glucosyltransferase (GTFA) enzyme (reuteransucrase). To gain insight into the reaction/product specificity of the GTFA enzyme and the mechanism of reuteran formation, incubations with Suc and/or a series of malto-oligosaccharides (MOSs) (degree of polymerization (DP2-DP6)) were followed in time. The structures of the initially formed products, isolated via high-performance anion-exchange chromatography, were analyzed by matrix-assisted laser-desorption ionization time-of-flight mass spectrometry and 1D/2D 1H/13C NMR spectroscopy. Incubations with Suc only, acting as both donor and acceptor, resulted in elongation of Suc with glucose (Glc) units via alternating (α1 → 4) and (α1 → 6) linkages, yielding linear gluco-oligosaccharides up to at least DP ~ 12. Simultaneously with the ensemble of oligosaccharides, polymeric material was formed early on, suggesting that alternan fragments longer than DP ~ 12 have higher affinity with the GTFA enzyme and are quickly extended, yielding high-molecular-mass branched reuteran (4 × 107 Da). MOSs (DP2-DP6) in the absence of Suc turned out to be poor substrates. Incubations of GTFA with Suc plus MOSs as substrates resulted in preferential elongation of MOSs (acceptors) with Glc units from Suc (donor). This apparently reflects the higher affinity of GTFA for MOSs compared with Suc. In accordance with the GTFA specificity, most prominent products were oligosaccharides with an (α1 → 4)/(α1 → 6) alternating structure. The Author 2013. Published by Oxford University Press.
First direct glycosylation of unprotected nonreducing mono- and disaccharides
Steinmann, Andreas,Thimm, Julian,Thiem, Joachim
, p. 5506 - 5513 (2008/09/17)
The first single-step random-glycosylation methodology for fully unprotected glycosyl acceptors is reported by random glycosylation leading to all possible regioisomers. For such systems conventional glycosylation methods such as Koenigs-Knorr glycosylation, Schmidt's trichloroacetimidate glycosylation and reactions employing glycosyl fluoride donors fail entirely. Starting from unprotected nonreducing saccharides, the glycosylation of β-glucosylated and β-galactosylated monosaccharides (Glc, Gal), symmetric disaccharides (e.g. α,α-trehaloses) as well as unsymmetric disaccharides (e.g. sucrose) were studied. The influence of base type and concentration were examined. Several libraries of di- and trisaccharides were generated. All regioisomers were formed in approximately equal proportions, and their partial separation was achieved by flash column chromatography. Even though it appears that overall yields are lower when comparing to classical protecting-group chemistry, this synthetic effort may be superior especially for access to higher saccharides. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
