Review
Structural control of cytochrome P450-catalyzed ω-hydroxylation

https://doi.org/10.1016/j.abb.2010.08.011Get rights and content

Abstract

The regiospecific or preferential ω-hydroxylation of hydrocarbon chains is thermodynamically disfavored because the ease of C–H bond hydroxylation depends on the bond strength, and the primary C–H bond of a terminal methyl group is stronger than the secondary or tertiary C–H bond adjacent to it. The hydroxylation reaction will therefore occur primarily at the adjacent secondary or tertiary C–H bond unless the protein structure specifically enforces primary C–H bond oxidation. Here we review the classes of enzymes that catalyze ω-hydroxylation and our current understanding of the structural features that promote the ω-hydroxylation of unbranched and methyl-branched hydrocarbon chains. The evidence indicates that steric constraints are used to favor reaction at the ω-site rather than at the more reactive (ω−1)-site.

Research highlights

Cytochrome P450 enzymes catalyze the ω-hydroxylation of unactivated hydrocarbon bonds. ► Hydroxylation is a difficult reaction that must be actively promoted by the enzyme. ► Cytochrome P450 enforces ω-hydroxylation by steric rather than electronic means.

Section snippets

Hydrocarbon ω-hydroxylation

In chemical terms, the regio- and stereoselective oxidation of unactivated hydrocarbon C–H bonds to the corresponding hydroxy (C–OH) products is the most difficult reaction catalyzed by cytochrome P450 enzymes. This substrate hydroxylation reaction is mediated by the “Compound I”-like ferryl species formed during the catalytic turnover of P450 enzymes. The Fe(IV) heme iron atom in this ferryl species is paired with a radical cation delocalized over the heme porphyrin ring, so the enzyme is two

Hydrocarbons

Bacterial P450 enzymes are known to oxidize linear hydrocarbons of C5–C15 chain lengths [11]. CYP153A1, identified in 2001 in Acinetobacter sp. EB104, was the first bacterial P450 specifically associated with this activity [12], but since then other members of the CYP153 family in diverse bacteria have been shown to catalyze the ω-hydroxylation of medium-length linear hydrocarbons [13], [14]. The ω-hydroxylation of hydrocarbons in bacteria enables them to grow on these compounds as their sole

CYP4 chain length tolerance

The relationship between fatty acid chain length and the hydroxylation regiospecificity of CYP4 enzymes has been extensively examined. The results of a typical study of rat CYP4A1, CYP4A2, CYP4A3, and CYP4A8, as well as human CYP4A11, shows that ω-regioselectivity tends to decrease for substrates longer than lauric acid (Table 2) [51]. A similar finding is obtained with rabbit CYP4A7, for which the fatty acid hydroxylation specificity gradually decreases from an ω/(ω−1)-ratio of 15.1 for lauric

Crystal structure of CYP124A1

The position in the M. tuberculosis genome of the gene coding for CYP124A1 adjacent to the gene for an enzyme that sulfates a terminal hydroxyl on a saturated isoprenoid chain led to the discovery that it catalyzes the ω-hydroxylation of branched hydrocarbon acids [39]. It has much lower activity for the oxidation of linear fatty acids and no detectable activity for the oxidation of branched or unbranched hydrocarbons (Table 3) [39]. Furthermore, the low activity for unbranched fatty acid

Conclusions

To achieve preferential ω-hydroxylation of hydrocarbon chains, cytochrome P450 enzymes must physically constrain their substrates so that the more facile (ω−1)-hydroxylations become disfavored. Analysis of all the ω-hydroxylation data indicates that this is achieved by steric interactions between the substrate and the protein residues rather than by an alteration of the reactivity of the ferryl species. The two crystal structures now available of M. tuberculosis enzymes that catalyze the

Acknowledgment

The preparation of this review and the experimental work at UCSF was supported by grants GM25515 and AI74824.

References (70)

  • H. Ouellet et al.

    Arch. Biochem. Biophys.

    (2010)
  • C.A. CaJacob et al.

    J. Biol. Chem.

    (1988)
  • F. Adas et al.

    J. Lipid Res.

    (1999)
  • Y. Miura et al.

    Biochim. Biophys. Acta

    (1975)
  • T. Maier et al.

    Biochem. Biophys. Res. Commun.

    (2001)
  • E.G. Funhoff et al.

    Enzyme Microb. Technol.

    (2007)
  • H.J.M. van den Brink et al.

    Fungal Genet. Biol.

    (1998)
  • U. Scheller et al.

    J. Biol. Chem.

    (1998)
  • M.B. Fisher et al.

    Biochem. Biophys. Res. Commun.

    (1998)
  • J.P. Hardwick

    Biochem. Pharmacol.

    (2008)
  • U. Hoch et al.

    Arch. Biochem. Biophys.

    (2000)
  • L.J. Roman et al.

    Arch. Biochem. Biophys.

    (1993)
  • I. Benveniste et al.

    Biochem. Biophys. Res. Commun.

    (1998)
  • J. Han et al.

    J. Biol. Chem.

    (2010)
  • R. Le Bouquin et al.

    Biochem. Biophys. Res. Commun.

    (1999)
  • I. Benveniste et al.

    Plant Sci.

    (2006)
  • T. Zimmer et al.

    Biochem. Biophys. Res. Commun.

    (1996)
  • D. Kim et al.

    Arch. Biochem. Biophys.

    (2007)
  • J.C. Komen et al.

    FEBS Lett.

    (2006)
  • T.J. Sontag et al.

    J. Lipid Res.

    (2007)
  • R.B. Bambal et al.

    Arch. Biochem. Biophys.

    (1996)
  • M. Norlin et al.

    J. Lipid Res.

    (2003)
  • D.L. Motola et al.

    Cell

    (2006)
  • J.K. Capyk et al.

    J. Biol. Chem.

    (2009)
  • K.J. McLean et al.

    J. Biol. Chem.

    (2009)
  • U. Hoch et al.

    Arch. Biochem. Biophys.

    (2000)
  • R.A. Kahn et al.

    Arch. Biochem. Biophys.

    (2001)
  • M. Hamberg et al.

    J. Biol. Chem.

    (1971)
  • X. Guan et al.

    Chem. Biol. Interact.

    (1998)
  • R.B. Bambal et al.

    Biochem. Biophys. Res. Commun.

    (1996)
  • D. Weissbart et al.

    Biochim. Biophys. Acta

    (1992)
  • M.A. Alterman et al.

    Biochem. Biophys. Res. Commun.

    (1995)
  • X. He et al.

    J. Biol. Chem.

    (2005)
  • P.R. Ortiz de Montellano et al.

    J. Biol. Chem.

    (1984)
  • A.S. Muerhoff et al.

    J. Biol. Chem.

    (1989)
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