Crystal Structures of Fe
            <sup>2+</sup>
            Dioxygenase Superoxo, Alkylperoxo, and Bound Product Intermediates

Kovaleva, Elena G.; Lipscomb, John D.

doi:10.1126/science.1134697

Cited by 360 publications

(521 citation statements)

References 24 publications

Supporting

Mentioning

485

Contrasting

Unclassified

Order By: Relevance

“…(C) Spectrum of Int-2. Red line is a spectral simulation using the parameters of Table 1. carbon (14). The calculated J value is small (J ¼ −5.8 cm −1 ), as observed experimentally (J ¼ þ6 cm −1 ), but ferromagnetic.…”

Section: Discussionsupporting

confidence: 79%

“…Note that the transient absorption feature at 610 nm that we associate with Int-1 is observed when H200N catalyzes either ring cleavage of HPCA or quinone formation from 4NC. In the mechanistic model we have proposed (Scheme 1), the reaction becomes committed to ring cleavage by superoxo radical attack on the substrate semiquinone to form the structurally characterized alkylperoxo intermediate (14). Most probably, the highly electron withdrawing nitro substituent of 4NC greatly decreases the rate of electron transfer to the Fe III -O 2 •− , especially in the absence of an acidbase catalyst and orienting residue at position 200.…”

Section: Discussionmentioning

confidence: 99%

“…In recent studies of the nonheme Fe II -containing homoprotocatechuate 2,3-dioxygenase (2,3-HPCD), we have shown that three intermediates of the catalytic cycle can be trapped in one crystal for structural analysis (14). One of these intermediates has been proposed to be an Fe II -superoxo species based on the long Fe-O bond distances and an unexpected lack of planarity of the aromatic ring of the alternative substrate 4-nitrocatechol (4NC), which chelates the iron in ligand sites adjacent to that of the O 2 .…”

mentioning

confidence: 99%

See 2 more Smart Citations

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Mbughuni

Chakrabarti

Hayden

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

146

297

View full text Add to dashboard Cite

Fe III -O 2 •− intermediates are well known in heme enzymes, but none have been characterized in the nonheme mononuclear Fe II enzyme family. Many steps in the O 2 activation and reaction cycle of Fe II -containing homoprotocatechuate 2,3-dioxygenase are made detectable by using the alternative substrate 4-nitrocatechol (4NC) and mutation of the active site His200 to Asn (H200N). Here, the first intermediate (Int-1) observed after adding O 2 to the H200N-4NC complex is trapped and characterized using EPR and Möss-bauer (MB) spectroscopies. Int-1 is a high-spin ( (1)(2)(3)(4)(5)(6)(7)(8). Internal electron transfer to form an Fe III -superoxo species converts the kinetically inert triplet ground state of O 2 to a doublet that can participate in the many types of chemistry characteristic of this mechanistically diverse group of enzymes. The same strategy is usually employed by heme-containing oxygenases and oxidases, leading in some cases to comparatively stable Fe III -superoxo intermediates that have been structurally and spectroscopically characterized (9-12). Instability of the putative superoxo intermediate in all mononuclear nonheme iron-containing enzymes has prevented similar characterization, although a superoxide level species has been reported for the dinuclear iron site of myo-inositol oxygenase (13).In recent studies of the nonheme Fe II -containing homoprotocatechuate 2,3-dioxygenase (2,3-HPCD), we have shown that three intermediates of the catalytic cycle can be trapped in one crystal for structural analysis (14). One of these intermediates has been proposed to be an Fe II -superoxo species based on the long Fe-O bond distances and an unexpected lack of planarity of the aromatic ring of the alternative substrate 4-nitrocatechol (4NC), which chelates the iron in ligand sites adjacent to that of the O 2 . In accord with the mechanism postulated for this enzyme class as illustrated in Scheme 1 (1, 8, 15-21), we have proposed that net electron transfer from 4NC through the Fe II to O 2 forms adjacent substrate and oxygen radicals (Scheme 1B). Recombination of the radicals would begin the ring cleavage and oxygen insertion reactions of this enzyme that eventually yield a muconic semialdehyde adduct as the product. A localized radical on the 4NC semiquinone at the incipient position of oxygen attack would account for the lack of ring planarity. Although this is the only structurally characterized nonheme Fe-superoxo species, the iron oxidation state differs from all of the other postulated Fe-superoxo intermediates.The mechanism that emerges from the structural and kinetic studies does not require a change in metal oxidation state to form a reactive intermediate (22). However, our studies of 2,3-HPCD in which Fe II is replaced with Mn II suggest that transient formaScheme 1. Proposed mechanism for extradiol dioxygenases. In the case of 2,3-HPCD, R is −CH 2 COO − and B is His200. When R is −NO 2 and His200 is changed to Asn, the reaction stalls before reaching intermediate C. Peroxide is slowly released a...

show abstract

Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Mbughuni

Chakrabarti

Hayden

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

146

297

View full text Add to dashboard Cite

show abstract

“…The calculated activation free energy of 23.3 kcal/mol is in a good agreement with the experimental barrier of 21 kcal/mol. The involvement of a peroxo intermediate in both intra-and extradiol cleavage reactions is supported by a number of computational studies [5,7,8,32] and by recent experimental studies of Kovaleva et al [3,4], where such an intermediate was actually detected. The peroxide O-O bond cleaves homolytically to give a radical Fe(IV)-oxo intermediate RAD.…”

Section: Discussionmentioning

confidence: 80%

DFT Study on the Catalytic Reactivity of a Functional Model Complex for Intradiol-Cleaving Dioxygenases

et al. 2010

View full text Add to dashboard Cite

The enzymatic ring-cleavage of catechol derivatives is catalyzed by two groups of dioxygenases, extradiol-and intradiol-cleaving dioxygenases. Although having a different oxidation state of their non-heme iron site and a different ligand coordination, both groups of enzymes involve a common peroxy intermediate in their catalytic cycle. The factors that lead to either extradiol cleavage resulting in 2-hydroxymuconaldehyde, or intradiol cleavage resulting in muconic acid, are not fully understood. Well characterized model compounds that mimic the functionality of these enzymes offer a basis for direct comparison to theoretical results. In this study the mechanism of a biomimetic iron complex is investigated with Density Functional Theory (DFT). This complex catalyzes the ring opening of catecholate with exclusive formation of the intradiol cleaved product. Several spin states are possible for the transition metal system, with the quartet state found to be of main importance during the reaction course. The mechanism investigated provides an explanation for the observed selectivity of the complex. First, a bridging peroxide is formed, which decomposes to an alkoxy-radical by O-O homolysis. In contrast to the subsequent barrier-free intradiol C-C bond cleavage, the extradiol pathway proceeds via the formation of an epoxide, which requires an additional activation barrier.

show abstract

“…76 and computational studies. 23,24 We tried to find such a side-on species also for SDO, but without any success.…”

Section: Resultsmentioning

confidence: 99%

O₂ Activation in Salicylate 1,2-Dioxygenase: A QM/MM Study Reveals the Role of His162

Dong

Ryde

2016

Inorg. Chem.

View full text Add to dashboard Cite

show abstract

Crystal Structures of Fe ²⁺ Dioxygenase Superoxo, Alkylperoxo, and Bound Product Intermediates

Cited by 360 publications

References 24 publications

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

DFT Study on the Catalytic Reactivity of a Functional Model Complex for Intradiol-Cleaving Dioxygenases

O₂ Activation in Salicylate 1,2-Dioxygenase: A QM/MM Study Reveals the Role of His162

Contact Info

Product

Resources

About

Crystal Structures of Fe 2+ Dioxygenase Superoxo, Alkylperoxo, and Bound Product Intermediates

Cited by 360 publications

References 24 publications

Trapping and spectroscopic characterization of an FeIII-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Trapping and spectroscopic characterization of an FeIII-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

DFT Study on the Catalytic Reactivity of a Functional Model Complex for Intradiol-Cleaving Dioxygenases

O2 Activation in Salicylate 1,2-Dioxygenase: A QM/MM Study Reveals the Role of His162

Contact Info

Product

Resources

About

Crystal Structures of Fe ²⁺ Dioxygenase Superoxo, Alkylperoxo, and Bound Product Intermediates

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

O₂ Activation in Salicylate 1,2-Dioxygenase: A QM/MM Study Reveals the Role of His162