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. 2012 Mar 7;134(9):4053-6.
doi: 10.1021/ja211905e. Epub 2012 Feb 22.

A single-site mutation (F429H) converts the enzyme CYP 2B4 into a heme oxygenase: a QM/MM study

Dandamudi Usharani  1 , Costantino Zazza, Wenzhen Lai, Mukesh Chourasia, Lucy Waskell, Sason Shaik
Affiliations

A single-site mutation (F429H) converts the enzyme CYP 2B4 into a heme oxygenase: a QM/MM study

Dandamudi Usharani et al. J Am Chem Soc. .

Abstract

The intriguing deactivation of the cytochrome P450 (CYP) 2B4 enzyme induced by mutation of a single residue, Phe429 to His, is explored by quantum mechanical/molecular mechanical calculations of the O-OH bond activation of the (Fe(3+)OOH)(-) intermediate. It is found that the F429H mutant of CYP 2B4 undergoes homolytic instead of heterolytic O-OH bond cleavage. Thus, the mutant acquires the following characteristics of a heme oxygenase enzyme: (a) donation by His429 of an additional NH---S H-bond to the cysteine ligand combined with the presence of the substrate retards the heterolytic cleavage and gives rise to homolytic O-OH cleavage, and (b) the Thr302/water cluster orients nascent OH(•) and ensures efficient meso hydroxylation.

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Figures

Figure 1
Figure 1
B3LYP optimized geometries (Å and degrees), and doublet-quartet energy gap, ,ΔE (kcal/mol) of Cpd 0 in the conformations LW1 (a) and LM1 (b). Note the NH---S H-bond in (b).
Figure 2
Figure 2
Key bond distances (Å) of the QM region in TSO-O (het) of the WT conformations LW1 (a) and LW3 (b).
Figure 3
Figure 3
Key bond distances (Å) in TSO-O (hom) and TSO-O (het) of the MT conformations, LM1 (a) LM2 (b) LM3 (c), and the homolytic intermediate point IH of LM3 (d).
Scheme 1
Scheme 1
The conversion of Cpd 0 to Cpd I vs. the HO option of generating a hydroxylated heme
Scheme 2
Scheme 2
Generic energy profiles starting from Cpd 0 (in its doublet ground state) and leading to Cpd I (to the right) and/or to meso-hydroxylation HO activity (to the left)
Scheme 3
Scheme 3
Electronic shift diagrams during O-OH cleavage of 2Cpd 0 in (a), during PCET and OH expulsion past 2TSO-O in (b), and the electronic configuration of 2Cpd I (c) and 2Heme-OH products (d).
Scheme 4
Scheme 4
Qualitative molecular orbital diagrams of mixing of the sulfur hybrid into the a2u orbital in WT (a) and MT (b)
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