ENZYMATIC SYNTHESIS AND REACTIONS OF A SUCROSE ISOMER α-d-GALACTOPYRANOSYL-β-d-FRUCTOFURANOSIDE

Towards tailor-made oligosaccharides-chemo-enzymatic approaches by enzyme and substrate engineering

Carbohydrate structures have been identified in eukaryotic and prokaryotic cells as glycoconjugates with communication skills. Their recently discussed role in various diseases has attracted high attention in the development of simple and convenient methods for oligosaccharide synthesis. In this review, recent approaches combining nature's power for the design of tailor made biocatalysts by enzyme engineering and substrate engineering will be presented. These strategies lead to highly efficient and selective glycosylation reactions. The introduced concept shall be a first step in the direction to a glycosylation toolbox which paves the way for the tailor-made synthesis of designed carbohydrate structures.

Investigations of the transfructosylation reaction by fructosyltransferase from B. subtilis NCIMB 11871 for the synthesis of the sucrose analogue galactosyl-fructoside

The exo-fructosyltransferase produced from B. subtilis NCIMB 11871 strain transfers the fructose moiety from donor alpha12 linked saccharides such as sucrose, raffinose and stachyose to the acceptor d-galactose, leading to the sucrose analogue, galactosyl-fructoside. Here, we report detailed kinetic studies. The enzyme showed a remarkably high optimal temperature at 50 degrees C and was effectively immobilised on Eupergit C 250 L and Trisopor-Amino. This is also the first report about the equilibrium of the transfructosylation reaction, its activation energy determination, the structure of the product and its preparative scale isolation.

Neisseria perflava amylosucrase: characterization of its product polysaccharide and a study of its inhibition by sucrose derivatives

Neisseria perflava amylosucrase forms from sucrose a polysaccharide very similar to glycogen, except that a larger proportion of its D-glucosyl residues are in short branches. Iodine staining of samples taken during polysaccharide formation indicate that the initial product is less branched than that formed at longer times. This glycogen-like polysaccharide has an estimated molecular mass range of 1 MD to 20 MD. Sucrose derivatives modified at C-3 (3-deoxysucrose and alpha-D-allopyranosyl beta-D-fructofuranoside), C-6 (6-deoxysucrose and 6-deoxy-6-fluorosucrose), and both C-4 and C-6 (4,6-dideoxysucrose) were tested as inhibitors of amylosucrase. Derivatives modified at C-6 were potent competitive inhibitors, with Ki values of 6.2 +/- 0.3 mM (6-deoxysucrose) and 0.50 +/- 0.06 mM (6-deoxy-6-fluorosucrose). The KM value of sucrose is 26.5 +/- 4.6 mM. Sucrose derivatives modified at C-3 were not significantly inhibitory over the concentration range tested. 4,6-Dideoxysucrose gave an unusual, non-competitive inhibition, in that, increasing its concentration did not produce a commensurate increase in the level of inhibition, which instead appeared to approach a limit. None of these sucrose derivatives was a substrate for amylosucrase, nor were they glycosyl donors to maltotriose.

Inhibition- and acceptor-reaction studies of Streptococcus mutans 6715 glucosyltransferases with 3-deoxysucrose, 3-deoxy-3-fluorosucrose, and alpha-D-allopyranosyl beta-D-fructofuranoside

Three new sucrose analogs modified at C-3 have been studied as inhibitors and substrates for the glucosyltransferases (glucansucrases) of Streptococcus mutans 6715. Although none of the analogs were found to be substrates for polymer synthesis with either the soluble-polysaccharide producing enzyme, GTF-S, or the insoluble-polysaccharide producing enzyme, GTF-I, 3-deoxysucrose and 3-deoxy-3-fluorosucrose were able to donate glycosyl residues for acceptor reactions with both enzymes. Modification at C-3 considerably decreased the binding at the active site of both enzymes, since all of the analogs had inhibition constants at least one order of magnitude greater than the Km value for sucrose.