Widboom Paul F, Fielding Elisha N, Liu Ye, Bruner Steven D
Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Nature. 2007 May 17;447(7142):342-5. doi: 10.1038/nature05702.
Enzyme-catalysed oxidations are some of the most common transformations in primary and secondary metabolism. The vancomycin biosynthetic enzyme DpgC belongs to a small class of oxygenation enzymes that are not dependent on an accessory cofactor or metal ion. The detailed mechanism of cofactor-independent oxygenases has not been established. Here we report the first structure of an enzyme of this oxygenase class in complex with a bound substrate mimic. The use of a designed, synthetic substrate analogue allows unique insights into the chemistry of oxygen activation. The structure confirms the absence of cofactors, and electron density consistent with molecular oxygen is present adjacent to the site of oxidation on the substrate. Molecular oxygen is bound in a small hydrophobic pocket and the substrate provides the reducing power to activate oxygen for downstream chemical steps. Our results resolve the unique and complex chemistry of DpgC, a key enzyme in the biosynthetic pathway of an important class of antibiotics. Furthermore, mechanistic parallels exist between DpgC and cofactor-dependent flavoenzymes, providing information regarding the general mechanism of enzymatic oxygen activation.
酶催化氧化是初级和次级代谢中一些最常见的转化反应。万古霉素生物合成酶DpgC属于一小类不依赖辅助因子或金属离子的氧化酶。不依赖辅因子的加氧酶的详细机制尚未明确。在此，我们报道了该类加氧酶中一种酶与结合的底物类似物复合物的首个结构。使用设计合成的底物类似物能够对氧激活的化学过程有独特的见解。该结构证实不存在辅因子，且在底物氧化位点附近存在与分子氧一致的电子密度。分子氧结合在一个小的疏水口袋中，底物提供还原能力以激活氧用于下游化学步骤。我们的结果解析了DpgC独特而复杂的化学性质，DpgC是一类重要抗生素生物合成途径中的关键酶。此外，DpgC与依赖辅因子的黄素酶之间存在机制上的相似之处，为酶促氧激活的一般机制提供了信息。
