Substrate-binding site of D-psicose 3-epimerase from Ruminococcus sp.

Abstract:

[Objective] The substrate-binding mechanism of D-psicose 3-epimerase from Ruminococcus sp. has been studied. [Methods] The residues involved in substrate-binding were selected using homology modelling and sequence alignment. Mutants were constructed by site-directed mutagenesis and studied by kinetic analysis. [Results] Two residues, Y6 and A109, were selected. Four mutants, Y6F, Y6I, A109P and A109L were constructed. [Conclusion] Y6 was involved in both catalysis and substrate-binding by the aromatic ring of the amino acid, while the -OH was important for substrate-binding. A109 was an important site that affected binding rather than catalyzing. This research would contribute to the study of catalytic mechanism and molecular modification of D-psicose (D-tagatose) 3-epimerase.