| 论文题目: | Crystal structures of D-psicose 3-epimerase from Clostridium cellulolyticum H10 and its complex with ketohexose sugars |
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| 作者: | Chan, HC; Zhu, YM; Hu, YM; Ko, TP; Huang, CH; Ren, FF; Chen, CC; Ma, YH; Guo, RT; Sun, YX |
| 联系作者: | Guo, RT |
| 刊物名称: | PROTEIN & CELL |
| 期: | 2 |
| 卷: | 3 |
| 页: | 123-131 |
| 年份: | 2012 |
| 影响因子: | |
| 论文下载: | |
| 摘要: | 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 (beta/alpha)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 ketohexose-bound 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. |
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