D-Psicose 3-epimerase(DPEase)is demonstrated to be useful in the bioproduction of D-psicose,a rare hexose sugar,from D-fructose,found plenty in nature.Clostridium cellulolyticum H10 has recently been identified as a D...D-Psicose 3-epimerase(DPEase)is demonstrated to be useful in the bioproduction of D-psicose,a rare hexose sugar,from D-fructose,found plenty in nature.Clostridium cellulolyticum H10 has recently been identified as a DPEase that can epimerize D-fructose to yield D-psicose with a much higher conversion rate when compared with the conventionally used DTEase.In this study,the crystal structure of the C.cellulolyticum DPEase was determined.The enzyme assembles into a tetramer and each subunit shows a(β/α)8 TIM barrel fold with a Mn2+metal ion in the active site.Additional crystal structures of the enzyme in complex with substrates/products(D-psicose,D-fructose,D-tagatose and D-sorbose)were also determined.From the complex structures of C.cellulolyticum DPEase with D-psicose and D-fructose,the enzyme has much more interactions with D-psicose than D-fructose by forming more hydrogen bonds between the substrate and the active site residues.Accordingly,based on these ketohexosebound complex structures,a C3-O3 proton-exchange mechanism for the conversion between D-psicose and D-fructose is proposed here.These results provide a clear idea for the deprotonation/protonation roles of E150 and E244 in catalysis.展开更多
基金by grants from Science and Technology Projects of Tianjin(No.10YFYBJC00100)National High Technology Research and Development Program of China(863 Project)(Grant No.2012AA021503)+1 种基金Visiting Professorships for Senior International Scientists(No.2010T1S4)One Hundred Talents Project of The Chinese Academy of Sciences to RTG.
文摘D-Psicose 3-epimerase(DPEase)is demonstrated to be useful in the bioproduction of D-psicose,a rare hexose sugar,from D-fructose,found plenty in nature.Clostridium cellulolyticum H10 has recently been identified as a DPEase that can epimerize D-fructose to yield D-psicose with a much higher conversion rate when compared with the conventionally used DTEase.In this study,the crystal structure of the C.cellulolyticum DPEase was determined.The enzyme assembles into a tetramer and each subunit shows a(β/α)8 TIM barrel fold with a Mn2+metal ion in the active site.Additional crystal structures of the enzyme in complex with substrates/products(D-psicose,D-fructose,D-tagatose and D-sorbose)were also determined.From the complex structures of C.cellulolyticum DPEase with D-psicose and D-fructose,the enzyme has much more interactions with D-psicose than D-fructose by forming more hydrogen bonds between the substrate and the active site residues.Accordingly,based on these ketohexosebound complex structures,a C3-O3 proton-exchange mechanism for the conversion between D-psicose and D-fructose is proposed here.These results provide a clear idea for the deprotonation/protonation roles of E150 and E244 in catalysis.