1883-12-1Relevant academic research and scientific papers
Regioselective oxidation of unprotected 1,4 linked glucans
Eisink, Niek N. H. M.,Lohse, Jonas,Witte, Martin D.,Minnaard, Adriaan J.
, p. 4859 - 4864 (2016)
Palladium-catalyzed alcohol oxidation allows the chemo- and regioselective modification of unprotected 1,4 linked glucans. This is demonstrated in the two-step bisfunctionalization of 1,4 linked glucans up to the 7-mer. Introduction of an anomeric azide is followed by a highly regioselective mono-oxidation of the terminal C3-OH functionality. The resulting orthogonal bis-functionalized oligosaccharides are a viable alternative to PEG-spacers as demonstrated in the conjugation of a cysteine mutant of 4-oxalocrotonate tautomerase with biotin.
Probing substrate promiscuity of amylosucrase from neisseria polysaccharea
Daude, David,Champion, Elise,Morel, Sandrine,Guieysse, David,Remaud-Simeon, Magali,Andre, Isabelle
, p. 2288 - 2295 (2013/08/23)
The amylosucrase from Neisseria polysaccharea (NpAS) naturally catalyzes the synthesis of a variety of products from sucrose and shows signs of plasticity of its active site. To explore further this promiscuity, the tolerance of amylosucrase towards different donor and acceptor substrates was investigated. The selection of alternate donor substrates was first made on the basis of preliminary molecular modeling studies. From 11 potential donors harboring selective derivatizations that were experimentally evaluated, only p-nitrophenyl-α-D-glucopyranoside was used by the wild-type enzyme, and this underlines the high specificity of the -1 subsite of NpAS for glucosyl donor substrates. The acceptor substrate promiscuity was further explored by screening 20 hydroxylated molecules, including D- and L-monosaccharides as well as polyols. With the exception of one compound, all were successfully glucosylated, and this showcases the tremendous plasticity of the +1 subsite of NpAS, which is responsible for acceptor recognition. The products obtained from the transglucosylation reactions of three selected acceptors were characterized, and they revealed original structures and enzyme enantiopreference, which were more particularly analyzed by insilico docking analyses.
Synthesis of sucrose analogues and the mechanism of action of Bacillus subtilis fructosyltransferase (levansucrase)
Seibel, Juergen,Moraru, Roxana,Goetze, Sven,Buchholz, Klaus,Na'amnieh, Shukrallah,Pawlowski, Alice,Hecht, Hans-Juergen
, p. 2335 - 2349 (2007/10/03)
In the present study, we have coupled detailed acceptor and donor substrate studies of the fructosyltransferase (FTF, levansucrase) (EC 2.4.1.162) from Bacillus subtilis NCIMB 11871, with a structural model of the substrate enzyme complex in order to investigate in detail the roles of the active site amino acids in the catalytic action of the enzyme and the scope and limitation of substrates. Therefore we have isolated the ftf gene, expressed in Escherichia coli, yielding a levansucrase. Consequently, detailed acceptor property effects in the fructosylation by systematic variation of glycoside acceptors with respect to the positions (2, 3, 4 and 6) of the hydroxyl groups from equatorial to axial have been studied for preparative scale production of new oligosaccharides. Such investigations provided mechanistic insights of the FTF reaction. The configuration and the presence of the C-2 and C-3 hydroxyl groups of the glucopyranoside derivatives either as substrates or acceptors have been identified to be rate limiting for the trans-fructosylation process. The rates are rationalized on the basis of the coordination of d-glycopyranoside residues in 4C1 conformation with a network of amino acids by Arg360, Tyr411, Glu342, Trp85, Asp247 and Arg246 stabilization of both acceptors and substrates. In addition we also describe the first FTF reaction, which catalyzes the β-(1→2)-fructosyl transfer to 2-OH of l-sugars (l-glucose, l-rhamnose, l-galactose, l-fucose, l-xylose) presumably in a 1C4 conformation. In those conformations, the l-glycopyranosides are stabilized by the same hydrogen network. Structures of the acceptor products were determined by NMR and mass spectrometry analysis.
