Models and Mechanisms of Cytochrome P450 Action

Groves, John T.; Han, Yuan-Zhang

doi:10.1007/978-1-4757-2391-5_1

Cited by 131 publications

(118 citation statements)

References 197 publications

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“…This is the critical intermediate and branch-point in P450 mechanisms where the control of proton delivery by the enzyme defines the catalytic results. Following second electron input to form a peroxo-anion adduct, protonation of the distal oxygen leads to hydroperoxo formation and ultimate oxygen-oxygen bond scission to form the higher valent metal-oxo complex commonly termed "Compound I" [8,12]. This pathway is thought to be operating in the first two steps of the aromatase reaction leading to the 19-aldehyde.…”

Section: Introductionmentioning

confidence: 99%

The ferrous-oxy complex of human aromatase

Grinkova

Denisov

Waterman

et al. 2008

Biochemical and Biophysical Research Communications

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In this communication, we document the self-assembly of heterologously expressed truncated human aromatase (CYP19) into nanometer scale phospholipids bilayers (Nanodiscs). The resulting P450 CYP19 preparation is stable, and can tightly associate the substrate androstenedione to form a nearly complete high-spin ferric protein. Ferrous CYP19 in Nanodiscs was mixed anaerobically in a rapidscan stopped-flow with atmospheric dioxygen and the formation of the ferrous-oxy complex observed. First order decay of the oxy-complex to release superoxide and regenerate the ferric enzyme was monitored kinetically. Surprisingly, the ferrous-oxy complex of aromatase is more stable that of hepatic CYP3A4, opening the path to precisely determine the biochemical and biophysical properties of the reaction cycle intermediates in this important human drug target.

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Section: Introductionmentioning

confidence: 99%

The ferrous-oxy complex of human aromatase

Grinkova

Denisov

Waterman

et al. 2008

Biochemical and Biophysical Research Communications

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“…The enzymes have attracted much interest because the heterolytic O±O bond scission of the heme-bound dioxygen and the C±H bond activation of inactivated hydrocarbons are difficult in mild conditions [1,5]. As the enzymes have an anionic thiolate as the axial heme ligand [6,7], the strong electron donation of the thiolate is supposed to facilitate the heterolysis of the dioxygen that coordinates trans to the thiolate ligand [8,9].…”

mentioning

confidence: 99%

Proximal cysteine residue is essential for the enzymatic activities of cytochrome P450cam

Shiro¹,

Takahashi²,

Hori³

et al. 2001

Eur J Biochem

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To investigate the functional and structural roles of the proximal thiolate ligand in cytochrome P450 cam , we prepared the C357H mutant of the enzyme in which the axial cysteine residue (Cys357) was replaced with a histidine residue. We obtained the unstable C357H mutant by developing a new preparation procedure involving in vitro folding of P450 cam from the inclusion bodies. The C357H mutant in the ferrous-CO form exhibited the Soret peak at 420 nm and the Fe-CO stretching line at 498 cm 21 , indicating a neutral histidine residue as the axial ligand. However, another internal ligand is coordinated to the heme iron as the sixth ligand in the ferric and ferrous forms of the C357H mutant, suggesting the collapse of the substratebinding site. The C357H mutant showed no catalytic activity for camphor hydroxylation and the reduced heterolytic/ homolytic ratio of the O±O bond scission in the reaction with cumene hydroperoxide. The present observations indicate that the thiolate coordination in P450 cam is important for the construction of the heme pocket and the heterolysis of the O±O bond.Keywords: P450; CPO; P420; oxygen activation; axial push effect.Heme-thiolate enzymes such as cytochrome P450 (P450) and chloroperoxidase from Caldariomyces fumago (CPO) activate heme-bound dioxygen and hydrogen peroxide and insert oxygen atoms into various hydrocarbons [1±4]. The enzymes have attracted much interest because the heterolytic O±O bond scission of the heme-bound dioxygen and the C±H bond activation of inactivated hydrocarbons are difficult in mild conditions [1,5]. As the enzymes have an anionic thiolate as the axial heme ligand [6,7], the strong electron donation of the thiolate is supposed to facilitate the heterolysis of the dioxygen that coordinates trans to the thiolate ligand [8,9]. The importance of the thiolate coordination for the activities of these enzymes is exemplified by their inactivated forms (P420 and C420) which lack the thiolate coordination [10,11]. However, the roles of Fe±S bond that are important to understand the molecular mechanism of the enzyme activities are still controversial [12,13].To clarify the roles of the thiolate coordination in the heme-thiolate enzymes, we replaced the axial histidine of myoglobin (Mb) with cysteine (H93C), and investigated its catalytic reactivities [14,15]. We observed that the thiolate ligand of Mb H93C accelerated the heterolysis of the O±O bond of cumene hydroperoxide and enhanced the hydrogen peroxide supported epoxidation of styrene [15]. These observations allowed us to propose that the thiolate ligation in heme proteins encourages the heterolytic cleavage of the O±O bond [15]. Our proposal is further confirmed by Higuchi et al. who demonstrated that the ligation of alkyl thiolate to iron porphyrin facilitates the O±O bond heterolysis of alkyl peracid in hydrophobic solvent [16,17]. These model works indicate the importance of the thiolate coordination in the heterolytic O±O bond scission.We have also shown experimentally that the thiolate ligand control...

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“…2.1 Basic structure and function of P450 enzymes Cytochrome P450 enzymes (P450s) efficiently utilize dioxygen to catalyze oxygenation in various biosyntheses of endogenous organic compounds and in detoxification of exogenous ones (Groves, 2005;Meunier et al, 2004). These enzymes constitute a large family of cysteinato-heme enzymes, are found in almost all forms of life, including bacteria, fungi, plants, insects, and mammals.…”

Section: Monooxygenase Cytochrome P450mentioning

confidence: 99%

Synthesis of Metallo-Deuteroporphyrin Derivatives and the Study of Their Biomimetic Catalytic Properties

Hu¹,

Sun²,

Xu³

et al. 2011

On Biomimetics

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Models and Mechanisms of Cytochrome P450 Action

Cited by 131 publications

References 197 publications

The ferrous-oxy complex of human aromatase

The ferrous-oxy complex of human aromatase

Proximal cysteine residue is essential for the enzymatic activities of cytochrome P450cam

Synthesis of Metallo-Deuteroporphyrin Derivatives and the Study of Their Biomimetic Catalytic Properties

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