β-Hydroxyalkyl σ-metalloporphyrins. Models for epoxide and alkene generation from cytochrome P-450

Dolphin, David; Matsumoto, A.; Shortman, Caroline

doi:10.1021/ja00183a084

Cited by 24 publications

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“…The results obtained in this study may comment to a limited extent on the mechanism of CPO-catalyzed epoxidation. In P450, the formation of organometallic porphyrin species during alkene epoxidation was originally proposed to explain exchange of the vinylic protons of propene with the aqueous medium under oxidizing conditions,9a although an alternate explanation for this result has since been offered 9b. We do not observe exchange of the vinylic protons of allylbenzene with water in heme-alkylated CPO and can thus exclude species with exchangeable protons as long-lived precursors to 8 .…”

Section: Discussionmentioning

confidence: 49%

“…In all alkene-modified heme systems studied to date, N -(2-hydroxyalkyl)porphyrins ( 1 ) containing the alkene skeleton (or their oxidized derivatives) 5c,e can be isolated from the epoxidation reaction following acid demetalation of the hemin. At least five distinct heme adducts might give rise to this chemistry: three metallocycles ( 2 − 4 ) with differing Fe,N bridge lengths; , a β-hydroxycarbene ( 5 ); and a σ-alkylhemin ( 6 ) …”

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confidence: 99%

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Structure of the Modified Heme in Allylbenzene-Inactivated Chloroperoxidase Determined by Q-Band CW and Pulsed ENDOR

et al. 1997

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During the epoxidation of allylbenzene, chloroperoxidase (CPO) is converted to an inactive green species in which the prosthetic heme has been modified by addition of the alkene plus an oxygen atom (Dexter, A. F.; Hager, L. P. J. Am. Chem. Soc. 1995, 117, 817−818). We have used Q-band continuous wave and pulsed electron-nuclear double resonance (ENDOR) spectroscopy to study the CPO heme in situ following inactivation with allylbenzene, using samples prepared in natural isotopic abundance, with 15N-labeled enzyme, and with allylbenzene labeled with 2H or 13C in specific vinylic positions. The electron paramagnetic resonance (EPR) spectrum of the inactivated enzyme is dominated by a low-spin ferric signal (g 1,2,3 = 2.32, 2.16, 1.95). 14,15N ENDOR examination of allylbenzene-inactivated CPO reveals that three nitrogens of the heme are similar, but the fourth nitrogen is markedly different, suggesting that a single pyrrole ring has been covalently modified at the unique nitrogen. These studies also reveal the orientation of the g tensor relative to the heme. 13C ENDOR of allylbenzene-inactivated CPO with 13C-labeled allylbenzene shows that the C-1 and C-2 carbons of allylbenzene are covalently connected to the heme system. 1,2H ENDOR plus mass analysis of CPO heme after inactivation with deuterated allylbenzene show that all three vinylic protons are retained in the heme adduct. No strongly-coupled exchangeable protons are observed, indicating that the axially bound water of frozen native CPO has been displaced. The 1H at the C-2 position of the alkene shows strong, mostly isotropic hyperfine coupling while the two hydrogens at the C-1 position show weak, dipolar couplings. The hyperfine tensors of 1,2H of the C-1 position of allylbenzene have been determined, and give the position of these atoms relative to the heme. These data, combined with molecular modeling calculations, have been used to deduce that the allylbenzene-bound heme of inactivated CPO is an N-alkylhemin metallocycle with C-1 of allylbenzene bonded to the pyrrole nitrogen and to obtain metrical details of its structure.

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Section: Discussionmentioning

confidence: 49%

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confidence: 99%

Structure of the Modified Heme in Allylbenzene-Inactivated Chloroperoxidase Determined by Q-Band CW and Pulsed ENDOR

et al. 1997

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“…9-19). Dolphin et al (1989) have prepared and studied the reactions of model J1-hydroxyalkyl a-metalloporphyrins ( Fig. 9-21).…”

Section: _3 Metabolism Of Halogenated Alkenesmentioning

confidence: 99%

“…A model ,B-hydroxyalkyl a-metalloporphyrin (Dolphin et a/., 1989). 261 have added much information on the nature of this important metabolic process.…”

Section: _3 Metabolism Of Halogenated Alkenesmentioning

confidence: 99%

Biochemistry of the Elemental Halogens and Inorganic Halides

Kirk

1991

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216

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Iron Porphyrin Chemistry

Walker¹,

Simonis²

2005

Encyclopedia of Inorganic Chemistry

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This article reviews most aspects of the chemistry of iron porphyrins, from Fe(0) to Fe(V), including occurrence and roles of natural iron porphyrins (hemes) and their synthetic analogs, structures and electron configurations of iron porphyrins of all oxidation and spin states, π electron configuration of the porphyrin ring, synthesis of metal‐free porphyrins and other related macrocycles, insertion of iron into free‐base porphyrins and related macrocycles, the properties, reactions, uses and biological relevance of iron(0), ‐(I), ‐(II) porphyrins (the latter with S = 0, 1, and 2 spin state possibilities), of iron(II) porphyrin π‐cation radicals, of iron(III) porphyrins (with S = 1/2, 3/2, and 5/2 spin state possibilities), of iron(III) porphyrin and corrole π‐cation radicals, of iron(IV) porphyrins (including five‐ and six‐coordinate ferryl (FeO) 2+ , iron(IV) phenyl, carbene and hydrazine complexes, and the bis‐methoxide complex) and a comparison of iron(IV) porphyrins to iron(III) porphyrin π‐cation radicals, of iron(IV) porphyrin π‐cation radicals, and of the possible existence of iron(V) porphyrins. Included in the Fe(II) part are sections on addition of ligands to four‐coordinate iron(II) porphyrins, including equilibrium binding constants, photodissociation of ligands from PFeL 2 complexes, binding of small molecules (O 2 , CO, NO, HNO) to 5‐coordinate iron(II) porphyrins and design of porphyrin ligands that will mimic the active sites of heme proteins such as myoglobin and hemoglobin, the cytochromes P450 and nitric oxide synthases, and the nitrophorins and guanylyl cyclases. Included in the iron(III) part are sections on both 5‐ and 6‐coordinate high‐spin complexes and their similarities and differences, bridged or through‐space magnetically coupled complexes of high‐spin iron(III) porphyrins with other metal complexes as possible models for cytochrome oxidase and the assimilatory sulfite reductases, coupled oxidation of hemes by hydrogen peroxide or its equivalent, and the relationship of this reactivity to the reactions of heme oxygenase, iron(III) porphyrins as reduction catalysts, and photochemistry of iron(III) porphyrins, possible electron configurations of low‐spin iron(III) porphyrins, the phenomenon and possible electronic consequences of ruffling of the porphinato core in iron(III) porphyrins, the preferred orientation of planar axial ligands bound to low‐spin iron(III) porphyrins, NO complexes of iron(III) porphyrins, reduction potentials, equilibrium constants and rates of axial‐ligand addition and exchange, kinetics of axial‐ligand rotation and porphyrin ring inversion, kinetics of reduction and autoreduction of iron(III) porphyrins, electron self‐exchange between low‐spin iron(III) and iron(II) porphyrins, synthetic ferriheme proteins, and synthesis of five‐coordinate low‐spin iron(III) porphyrins having σ‐alkyl or σ‐aryl groups as axial ligands. The iron(IV) and iron(IV) cation radical sections discuss the high‐valent states of cytochromes P450 and related enzymes.

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β-Hydroxyalkyl σ-metalloporphyrins. Models for epoxide and alkene generation from cytochrome P-450

Cited by 24 publications

References 1 publication

Structure of the Modified Heme in Allylbenzene-Inactivated Chloroperoxidase Determined by Q-Band CW and Pulsed ENDOR

Structure of the Modified Heme in Allylbenzene-Inactivated Chloroperoxidase Determined by Q-Band CW and Pulsed ENDOR

Biochemistry of the Elemental Halogens and Inorganic Halides

Iron Porphyrin Chemistry

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