Kells Petrea M, Ouellet Hugues, Santos-Aberturas Javier, Aparicio Jesus F, Podust Larissa M
Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.
Chem Biol. 2010 Aug 27;17(8):841-51. doi: 10.1016/j.chembiol.2010.05.026.
We present the X-ray structure of PimD, both substrate-free and in complex with 4,5-desepoxypimaricin. PimD is a cytochrome P450 monooxygenase with native epoxidase activity that is critical in the biosynthesis of the polyene macrolide antibiotic pimaricin. Intervention in this secondary metabolic pathway could advance the development of drugs with improved pharmacologic properties. Epoxidation by P450 typically includes formation of a charge-transfer complex between an oxoferryl pi-cation radical species (Compound I) and the olefin pi-bond as the initial intermediate. Catalytic and structural evidence presented here suggest that epoxidation of 4,5-desepoxypimaricin proceeds via a hydroperoxoferric intermediate (Compound 0). The oxygen atom of Compound 0 distal to the heme iron may insert into the double bond of the substrate to make an epoxide ring. Stereoelectronic features of the putative transition state suggest substrate-assisted proton delivery.
我们展示了无底物状态以及与4,5-去环氧匹马菌素形成复合物状态下的PimD的X射线结构。PimD是一种具有天然环氧化酶活性的细胞色素P450单加氧酶，在多烯大环内酯类抗生素匹马菌素的生物合成中至关重要。对这一次级代谢途径的干预可能会推动具有改善药理特性的药物的开发。细胞色素P450介导的环氧化反应通常包括在氧合铁π-阳离子自由基物种（化合物I）和烯烃π-键之间形成电荷转移复合物作为初始中间体。此处提供的催化和结构证据表明，4,5-去环氧匹马菌素的环氧化反应通过氢过氧铁中间体（化合物0）进行。化合物0中远离血红素铁的氧原子可能插入底物的双键中形成环氧环。假定过渡态的立体电子特征表明存在底物辅助的质子传递。
