| Popis: |
The characteristics and the application of recombinant sucrose synthase 1 (SuSy1) from potato for the synthesis of sucrose analogues are described. With UDP-Glc as donor substrate SuSy1 accepts a variety of ketoses, e.g., 1-deoxy-1-fluoro-D-fructose (6; 100%), L-sorbose (7, 55%), and D-xylulose (8; 42%), as well as aldoses, e.g., D-talose (15; 36%), D-idose (16; 24%), D-lyxose (12; 48%), L-arabinose (13; 36%), and D-ribose (14; 7%). Kinetic analyses revealed that the non-natural acceptors 6 (kcat/Km = 3.5 s −1 mM −1), 7 (kcat/Km = 1⋅10 −2 s −1 mM −1), 8 (kcat/Km = 2⋅10 −2 s −1 mM −1), and 12 (kcat/Km = 2⋅10 −2 s −1 mM −1) were relatively poor substrates when compared to D-fructose (5; kcat/Km = 34.1 s −1 mM −1). It is concluded that the configuration and/or presence of the hydroxymethyl group at C5 determine the affinity of the ketoses for SuSy1. The acceptance of aldoses can be explained by their flexible chair conformations, which lead to isosteric hydroxy groups recognized by SuSy1. The preparative synthesis of sucrose analogues yielded 1´-deoxy-1´-fluoro-β-D-fructofuranosyl-α-D-glucopyranoside (1), [ 13C1]-β-D-fructofuranosyl-α-D-glucopyranoside (2), α-D-glucopyranosyl-α-L-sorbofuranoside (3), and α-D-glucopyranosyl-α-D-lyxopyranoside (4), in a 0.1 − 1.0 g scale. The sucrose analogues 1, 3, and 4 were not hydrolyzed by invertase, which makes them valuable tools for studies on signal transduction pathways and sugar transport in plants. |
Plný text