Studies of the Oxidative Rearrangement Mechanism of pentalenolactone F by Cytochrome P450 PntM

【作者】 王西亚； 刘永军；

【机构】 山东大学理论化学研究所；

【摘要】 The cytochrome P450 CYP162C2（PntM） is responsible for the final step in the biosynthesis of the sesquiterpenoid antibiotic pentalenolactone.In this work,on the basis of the crystal structure of P450 PntM in complex with the substrate（pdb code:5 L10）,QM/MM calculations have been performed to predict the mechanism of the transformation from pentalenolactone F to pentalenolactone,which involves the stereospecific removal of the H-1 si of pentalenolactone F,syn-1,2-migration of the 2 si methyl group,and the antarafacial loss of H-3 re.Our calculation results indicate that the abstraction of the substrate hydrogen atom by porphyrin+·/Fe⁴⁺=O（Compound I） is the rate limiting step.Unlike other P450 s,following the hydrogen abstraction,the methyl transfer rather than the O-rebound is the dominate reaction,which correspond to energy barriers of 2.4 vs 20.4 kcal/mol,respectively.It is the steric hindrance at C1 of substrate that prevents the access of the heme-bound hydroxyl group to the si face of the C-1 radical.Calculation results and structural analysis demonstrate that the alternative deprotonation of the intermediates can generate isomeric rearrangement products（pentalenolactones A,B and P）.更多还原

【Abstract】 The cytochrome P450 CYP162C2（PntM） is responsible for the final step in the biosynthesis of the sesquiterpenoid antibiotic pentalenolactone.In this work,on the basis of the crystal structure of P450 PntM in complex with the substrate（pdb code:5 L10）,QM/MM calculations have been performed to predict the mechanism of the transformation from pentalenolactone F to pentalenolactone,which involves the stereospecific removal of the H-1 si of pentalenolactone F,syn-1,2-migration of the 2 si methyl group,and the antarafacial loss of H-3 re.Our calculation results indicate that the abstraction of the substrate hydrogen atom by porphyrin+·/Fe⁴⁺=O（Compound I） is the rate limiting step.Unlike other P450 s,following the hydrogen abstraction,the methyl transfer rather than the O-rebound is the dominate reaction,which correspond to energy barriers of 2.4 vs 20.4 kcal/mol,respectively.It is the steric hindrance at C1 of substrate that prevents the access of the heme-bound hydroxyl group to the si face of the C-1 radical.Calculation results and structural analysis demonstrate that the alternative deprotonation of the intermediates can generate isomeric rearrangement products（pentalenolactones A,B and P）.更多还原