2hk0
From Proteopedia
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Crystal structure of D-psicose 3-epimerase (DPEase) in the absence of substrate
Overview
D-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.
About this Structure
2HK0 is a Single protein structure of sequence from Agrobacterium tumefaciens. Full crystallographic information is available from OCA.
Reference
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
Page seeded by OCA on Tue Jan 29 20:22:41 2008
