Radical catalysis in Fe/S cluster dependent dehydratases

Fe/S 簇依赖性脱水酶中的自由基催化

• 批准号: 59573511
• 负责人: Professor Dr. Holger Dobbek
• 金额: --
• 依托单位: Arbeitsgruppe Strukturbiologie und Biochemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/59573511?language=en
• 关键词: Radical; catalysis; Fe; cluster; dependent

Typical dehydratases catalyze the cleavage of a carbon-oxygen bond yielding an unsaturated product via a,b-elimination of water. The a-hydrogen (pKa ~ 8) to be removed as proton is activated by an adjacent electron-withdrawing group, and the hydroxyl group leaves from the b-position. In contrast, several anaerobic bacteria employ oxygensensitive 2- or 4-hydroxyacyl-CoA dehydratases that use radicals to lower the pK of the unactivated b-protons by up to 26 units. These atypical dehydratases are the class of 2- hydroxyacyl-CoA dehydratases and the 4-hydroxybutyryl-CoA dehydratase. The former consist of two components: (a) a Fe/S-dependent ATPase component (activator) to generate the radical and (b) a Fe/S-dependent dehydratase catalyzing the actual dehydration. Recent spectroscopic investigations showed that a catalytically competent ketyl-radical anion is generated on the substrate to facilitate the dehydration. The research proposal focuses on elucidating the structural bases of (I.) nucleotide- and redox-dependent changes proposed for the activator, (II.) complex formation between the two components leading to radical generation on the dehydratase component and (III.) the unusual active site metal cluster of the dehydratase component. (IV.) Additionally, we want to extent our structural studies on the mechanism of 4-hydroxybutyryl-CoA dehydratases by studying substrate- and product-complexes.

典型的脱氢酶催化碳-氧键的裂解，通过a，b-消除水产生不饱和产物。作为质子被除去的α-氢（pKa ~ 8）被相邻的吸电子基团活化，羟基从b-位离开。相比之下，一些厌氧细菌使用氧敏感的2-或4-羟酰基-CoA脱氢酶，其使用自由基将未活化的b-质子的pK降低多达26个单位。这些非典型辅酶A氧化酶是2-羟酰基辅酶A氧化酶和4-羟丁酰基辅酶A氧化酶。前者由两种组分组成：（a）产生自由基的Fe/S依赖性ATP酶组分（活化剂）和（B）催化实际脱水的Fe/S依赖性ATP酶。最近的光谱研究表明，催化活性的酮基自由基阴离子上产生的基板上，以促进脱水。研究建议的重点是阐明（I）的结构基础。核苷酸和氧化还原依赖性的变化提出的激活剂，（II.）两种组分之间的复合物形成导致在所述酶组分上产生自由基，和（III.）不寻常的活性位点金属簇的酶组分。（四）此外，我们希望通过研究底物和产物复合物来扩展我们对4-羟基丁酰-CoA脱氢酶机制的结构研究。