2hk1
Crystal structure of D-psicose 3-epimerase (DPEase) in the presence of D-fructose
Structural highlights
FunctionDPES_AGRFC Involved in the biosynthesis of D-psicose. Catalyzes the reversible epimerization of D-fructose at the C3 position to yield D-psicose. The enzyme is highly specific for D-psicose and shows very low activity with D-tagatose. The substrate specificity decreases in the following order: D-fructose, D-tagatose, D-ribulose, D-xylulose, and D-sorbose. It shows a higher level of activity for cis ketoses than for trans-ketoses.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedD-psicose, a rare sugar produced by the enzymatic reaction of D-tagatose 3-epimerase (DTEase), has been used extensively for the bioproduction of various rare carbohydrates. Recently characterized D-psicose 3-epimerase (DPEase) from Agrobacterium tumefaciens was found to belong to the DTEase family and to catalyze the interconversion of D-fructose and D-psicose by epimerizing the C-3 position, with marked efficiency for D-psicose. The crystal structures of DPEase and its complex with the true substrate D-fructose were determined; DPEase is a tetramer and each monomer belongs to a TIM-barrel fold. The active site in each subunit is distinct from that of other TIM-barrel enzymes, which use phosphorylated ligands as the substrate. It contains a metal ion with octahedral coordination to two water molecules and four residues that are absolutely conserved across the DTEase family. Upon binding of D-fructose, the substrate displaces water molecules in the active site, with a conformation mimicking the intermediate cis-enediolate. Subsequently, Trp112 and Pro113 in the beta4-alpha4 loop undergo significant structural changes, sealing off the active site. Structural evidence and site-directed mutagenesis of the putative catalytic residues suggest that the metal ion plays a pivotal role in catalysis by anchoring the bound D-fructose, and Glu150 and Glu244 carry out an epimerization reaction at the C-3 position. Crystal structure of D-psicose 3-epimerase from Agrobacterium tumefaciens and its complex with true substrate D-fructose: a pivotal role of metal in catalysis, an active site for the non-phosphorylated substrate, and its conformational changes.,Kim K, Kim HJ, Oh DK, Cha SS, Rhee S J Mol Biol. 2006 Sep 1;361(5):920-31. Epub 2006 Jul 28. PMID:16876192[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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