Resonance Raman spectroscopy of the catalytic intermediates and derivatives of chloroperoxidase from Caldariomyces fumago.

Hosten, Charles M.; Sullivan, Ann; Palaniappan, Vaithianathan; Fitzgerald, Melissa M.; Terner, James

doi:10.1016/s0021-9258(17)36742-x

Cited by 51 publications

(36 citation statements)

References 89 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…INDO/S semiemprical calculations of a model compound I using the DFT porphine compound I geometry also result in a 2 A 2u ground state, in complete agreement with the DFT results reported in this work. While recent evidence from Raman spectroscopy indicates a 2 A 1u ground state for chloroperoxidase, there is no contradiction with the finding of a 2 A 2u ground state for the porphine compound I form in the present work. The disparity is not between computed and experimental results but in the heme sites involved.…”

Section: Resultscontrasting

confidence: 91%

“…With addition of porphyrin substituents corresponding to protoporphyrin IX in the intact proteins to the porphyrin ring in the optimized geometry derived from the DFT, the INDO/S ground state is a 2 A 1u ground state. 34 Thus, the observation of marker bands indicating a doublet 2 A 1u radical cation compound I porphyrin species in chloroperoxidase 33 is consistent with these results for a model system containing the same heme species.…”

Section: Discussionsupporting

confidence: 69%

See 1 more Smart Citation

Theoretical Investigation of the Proton Assisted Pathway to Formation of Cytochrome P450 Compound I

1998

View full text Add to dashboard Cite

Functional and dysfunctional enzymatic pathways of cytochrome P450s after formation of the reduced ferrous dioxygen species have been investigated using nonlocal density functional quantum chemical methods, employing a methyl mercapto iron porphine model of the cytochrome P450 heme complex. The goal of this study was to assess the validity of proposed pathways to both compound I and peroxide involving protonation of the distal and proximal oxygen atoms of the reduced ferrous dioxygen species. Optimized geometries, energies, and electrostatic and electronic properties of each putative heme intermediate in these pathways were calculated and these properties examined for consistency with the proposed role of the intermediate in compound I or peroxide formation. Single protonation of the distal oxygen resulted in significant weakening of the O-O bond. Addition of a second proton to the distal oxygen and energy optimization led directly to compound I and water products, without any apparent activation barrier or formation of a diprotonated intermediate. These results provide direct robust support for the proton-assisted mechanism of dioxygen bond cleavage to form compound I. The dysfunctional pathway to the formation of peroxide was explored by examining the properties of the distal and proximal singly protonated species. The proximal tautomer is thermodynamically less favorable than the distal species by 18.4 kcal/mol. Electrostatic features of both singly protonated species suggest preferred proton delivery to the remaining unprotonated oxygen in each case, favoring peroxide formation. Moreover, addition of a second proton to either of these singly protonated species results in formation of a stable hydrogen peroxide heme complex. These results, taken together, suggest that the simultaneous availability of two protons on the distal oxygen is a requirement for P450 enzymatic efficacy, while asynchronous delivery of protons to the dioxygen site favors decoupling.

show abstract

Section: Resultscontrasting

confidence: 91%

Section: Discussionsupporting

confidence: 69%

Theoretical Investigation of the Proton Assisted Pathway to Formation of Cytochrome P450 Compound I

1998

View full text Add to dashboard Cite

show abstract

“…This prevents the correlation of these vibrations to a well-defined geometrical change of the heme cofactor. Furthermore, only a few oxygen-related vibrations have been determined for these three enzymes (25,(52)(53)(54)(55)(56)(57), and a full analysis of the effect of the proximal thiolate on the reactivity of oxygen intermediates, as for histidine (8),…”

Section: Discussionmentioning

confidence: 99%

Resonance Raman Detection of the Fe−S Bond in Endothelial Nitric Oxide Synthase^,

et al. 2002

View full text Add to dashboard Cite

We report the first low-frequency resonance Raman spectra of ferric endothelial nitric oxide synthase (eNOS) holoenzyme, including the frequency of the Fe-S vibration in the presence of the substrate L-arginine. This is the first direct measurement of the strength of the Fe-S bond in NOS. The Fe-S vibration is observed at 338 cm(-1) with excitation at 363.8 nm. The assignment of this band to the Fe-S stretching vibration was confirmed by the observation of isotopic shifts in eNOS reconstituted with 54Fe- and 57Fe-labeled hemin. Furthermore, the frequency of this vibration is close to those observed in cytochrome P450(cam) and chloroperoxidase (CPO). The frequency of this vibration is lower in eNOS than in P450(cam) and CPO, which can be explained by differences in hydrogen bonding to the proximal cysteine heme ligand. On addition of substrate to eNOS, we also observe several low-frequency vibrations, which are associated with the heme pyrrole groups. The enhancement of these vibrations suggests that substrate binding results in protein-mediated changes of the heme geometry, which may provide the protein with an additional tuning element for the redox potential of the heme iron. The implications of our findings for the function of eNOS will be discussed by comparison with P450(cam) and model compounds.

show abstract

“…Cytochrome P450 Compound I has not been detected unambiguously due to its high reactivity, although there is indirect evidence for its existence. 8,9 Experimental observations [10][11][12] on CPO-Compound I suggest that it has a doublet ground state with two parallel unpaired electrons on the iron-oxo moiety and an antiparallel electron in a p-orbital of the porphyrin ligand. Theoretical studies [13][14][15][16][17][18][19][20] predict that the ground state of Compound I in the protein is a quasi-degenerate pair of triradicaloid states, labelled 2 A 2u and 4 A 2u .…”

Section: Introductionmentioning

confidence: 99%

Mechanism and structure–reactivity relationships for aromatic hydroxylation by cytochrome P450

Ridder²,

et al. 2004

View full text Add to dashboard Cite

Cytochrome P450 enzymes play a central role in drug metabolism, and models of their mechanism could contribute significantly to pharmaceutical research and development of new drugs. The mechanism of cytochrome P450 mediated hydroxylation of aromatics and the effects of substituents on reactivity have been investigated using B3LYP density functional theory computations in a realistic porphyrin model system. Two different orientations of substrate approach for addition of Compound I to benzene, and also possible subsequent rearrangement pathways have been explored. The rate-limiting Compound I addition to an aromatic carbon atom proceeds on the doublet potential energy surface via a transition state with mixed radical and cationic character. Subsequent formation of epoxide, ketone and phenol products is shown to occur with low barriers, especially starting from a cation-like rather than a radical-like tetrahedral adduct of Compound I with benzene. Effects of ring substituents were explored by calculating the activation barriers for Compound I addition in the meta and para-position for a range of monosubstituted benzenes and for more complex polysubstituted benzenes. Two structure-reactivity relationships including 8 and 10 different substituted benzenes have been determined using (i) experimentally derived Hammett sigma-constants and (ii) a theoretical scale based on bond dissociation energies of hydroxyl adducts of the substrates, respectively. In both cases a dual-parameter approach that employs a combination of radical and cationic electronic descriptors gave good relationships with correlation coefficients R2 of 0.96 and 0.82, respectively. These relationships can be extended to predict the reactivity of other substituted aromatics, and thus can potentially be used in predictive drug metabolism models.

show abstract

Resonance Raman spectroscopy of the catalytic intermediates and derivatives of chloroperoxidase from Caldariomyces fumago.

Cited by 51 publications

References 89 publications

Theoretical Investigation of the Proton Assisted Pathway to Formation of Cytochrome P450 Compound I

Theoretical Investigation of the Proton Assisted Pathway to Formation of Cytochrome P450 Compound I

Resonance Raman Detection of the Fe−S Bond in Endothelial Nitric Oxide Synthase^,

Mechanism and structure–reactivity relationships for aromatic hydroxylation by cytochrome P450

Contact Info

Product

Resources

About

Resonance Raman spectroscopy of the catalytic intermediates and derivatives of chloroperoxidase from Caldariomyces fumago.

Cited by 51 publications

References 89 publications

Theoretical Investigation of the Proton Assisted Pathway to Formation of Cytochrome P450 Compound I

Theoretical Investigation of the Proton Assisted Pathway to Formation of Cytochrome P450 Compound I

Resonance Raman Detection of the Fe−S Bond in Endothelial Nitric Oxide Synthase,

Mechanism and structure–reactivity relationships for aromatic hydroxylation by cytochrome P450

Contact Info

Product

Resources

About

Resonance Raman Detection of the Fe−S Bond in Endothelial Nitric Oxide Synthase^,