Oxy Intermediates of Homoprotocatechuate 2,3-Dioxygenase: Facile Electron Transfer between Substrates

Mbughuni, Michael M.; Chakrabarti, Mrinmoy; Hayden, Joshua A.; Meier, Katlyn K.; Dalluge, Joseph J.; Hendrich, Michael P.; Münck, Eckard; Lipscomb, John D.

doi:10.1021/bi201436n

Cited by 47 publications

(119 citation statements)

References 42 publications

Supporting

Mentioning

110

Contrasting

Unclassified

Order By: Relevance

“…44,46 Since initial submission of this work, the equivalent intermediate for the native substrate HPCA (H200N-HPCA Int1 ) has also been trapped and spectroscopically characterised. 21 The M€ ossbauer parameters (d ¼ 0.48 and DE Q ¼ 0.95) are similar to those measured for the slow substrate. This intermediate is found to contain high-spin Fe III antiferromagnetically coupled to a radical, which is most likely substrate based, 21 and is assigned as a Fe III -(hydro)peroxo bound to a semiquinone level ligand, entirely consistent with the electronic structure predicted here for the hydroperoxo species.…”

Section: Hydroperoxidesupporting

confidence: 65%

“…This observation has led to the suggestion that since the reactivity is not dependent on the redox potential of the metal, oxygen activation and substrate oxidation occurs without a change in metal oxidation state. 11,12,21 Instead of a redox change, it is proposed that the metal simply assists in the transfer of the electrons from the substrate to O 2 . This proposal is supported by a density functional theory (DFT) study which suggested that the +2 oxidation state is maintained through the peroxo-bridge formation up until O-O cleavage.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Oxygen activation in extradiol catecholate dioxygenases – a density functional study

Christian

Ye²,

Neese³

2012

Chem. Sci.

119

View full text Add to dashboard Cite

Recent trapping and spectroscopic characterization of an O 2 adduct for the non-heme enzyme homoprotocatechuate 2,3-dioxygenase (HPCD) demonstrates it to be a Fe III -superoxo species. This proposal is in direct opposition to the consensus mechanism (., Proc. Natl. Acad. Sci. U. S. A., 2008, 105, 7347-7352) in which the metal facilitates the transfer of electrons from the substrate to O 2 to form the reactive species in the mechanism without changing oxidation state. In this study we performed a detailed analysis of the electronic structure of the O 2 adduct for the mutant and native enzymes and the nature of oxygen activation in the reaction mechanism of HPCD using a combination of computational chemistry and theoretical M€ ossbauer spectroscopy. Our results are in agreement with the available experimental data and demonstrate that even for the native enzyme changes in the metal oxidation state are an important factor in oxygen activation.

show abstract

Section: Hydroperoxidesupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Oxygen activation in extradiol catecholate dioxygenases – a density functional study

Christian

Ye²,

Neese³

2012

Chem. Sci.

119

View full text Add to dashboard Cite

show abstract

“…Ringcleaving dioxygenases active toward these noncatecholic compounds belong to the cupin superfamily and utilize a mononuclear Fe II center for catalysis. Their catalytic strategy has been proposed to involve a one-electron transfer to dioxygen, possibly via transient formation of an Fe III -O 2 · Ϫ intermediate, as observed in type I extradiol dioxygenases (83,84), which are members of the VOC superfamily (5). However, it should be emphasized that compared to the thoroughly studied extradiol dioxygenase reaction mechanism, much less experimental evidence is available on the catalytic mechanism of the cupin-type ring-cleaving dioxygenases.…”

Section: Discussionmentioning

confidence: 99%

“…Subsequent rearrangement and O-O bond cleavage gives a seven-membered lactone intermediate and an Fe II -bound hydroxide ion, which hydrolyzes the lactone to yield the 2-hydroxymuconate semialdehyde product (Fig. 1b) (44,71,72,78,83,84).…”

mentioning

confidence: 99%

Ring-Cleaving Dioxygenases with a Cupin Fold

Fetzner

2012

Appl Environ Microbiol

166

141

View full text Add to dashboard Cite

ABSTRACTRing-cleaving dioxygenases catalyze key reactions in the aerobic microbial degradation of aromatic compounds. Many pathways converge to catecholic intermediates, which are subject toorthoormetacleavage by intradiol or extradiol dioxygenases, respectively. However, a number of degradation pathways proceed via noncatecholic hydroxy-substituted aromatic carboxylic acids like gentisate, salicylate, 1-hydroxy-2-naphthoate, or aminohydroxybenzoates. The ring-cleaving dioxygenases active toward these compounds belong to the cupin superfamily, which is characterized by a six-stranded β-barrel fold and conserved amino acid motifs that provide the 3His or 2- or 3His-1Glu ligand environment of a divalent metal ion. Most cupin-type ring cleavage dioxygenases use an FeIIcenter for catalysis, and the proposed mechanism is very similar to that of the canonical (type I) extradiol dioxygenases. The metal ion is presumed to act as an electron conduit for single electron transfer from the metal-bound substrate anion to O2, resulting in activation of both substrates to radical species. The family of cupin-type dioxygenases also involves quercetinase (flavonol 2,4-dioxygenase), which opens up two C-C bonds of the heterocyclic ring of quercetin, a wide-spread plant flavonol. Remarkably, bacterial quercetinases are capable of using different divalent metal ions for catalysis, suggesting that the redox properties of the metal are relatively unimportant for the catalytic reaction. The major role of the active-site metal ion could be to correctly position the substrate and to stabilize transition states and intermediates rather than to mediate electron transfer. The tentative hypothesis that quercetinase catalysis involves direct electron transfer from metal-bound flavonolate to O2is supported by model chemistry.

show abstract

“…My student Stephanie Groce showed that mutation of the active site's histidine 200 to any of several other amino acids greatly slowed the turnover of 4-NC and HPCA, so intermediates could potentially be trapped (38). Finally, Michael Mbughuni used a newly developed rapid freeze quench (RFQ) device to trap intermediates from reaction of the variants with 4-NC and other substrates for EPR and Mössbauer studies (39,40). Similar studies revealed the role of tyrosine 257 in distorting the aromatic ring of the substrate to promote electron transfer to the O 2 (41,42).…”

Section: Slowly Finding Transient Intermediates In Dioxygenasesmentioning

confidence: 99%

Life in a Sea of Oxygen

Lipscomb¹

2014

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Learning to ListenD uring my third week of high school chemistry, our instructor left in the middle of class in obvious pain and passed away shortly thereafter. This sad event could have spelled disaster for a budding career in chemistry, except for the fact that it occurred at Brandywine High School near Wilmington, Delaware, where 2,500 Ph.D. chemists lived in the school district. These included my father, Robert D. Lipscomb, who, like so many of his DuPont Central Research & Development colleagues, was a product of the Roger Adams/Reynold Fuson/Carl "Speed" Marvel/John Bailar, Jr., era at the University of Illinois. Chemistry class was taken over in principle by a substitute, who was an excellent football coach but knew little chemistry. In fact, it became a learning experiment, fed vicariously by a community of nearly unparalleled depth of expertise and, as I came to experience for the first time, an inbred commitment to understanding over learning. Our fathers and mothers taught us every night, and we taught each other in class. We learned to hear how others interpreted the principles of chemistry and to evaluate quickly how this fit into our own framework for understanding. I have used these lessons, both the importance of listening and the commitment to the profession, continuously in the fifty years that have since passed. I have encountered them in one form or another in each of my mentors. My graduate school advisor I. C. "Gunny" Gunsalus said it very concisely: "Science is about 'learning to listen'." Learn to listen to what your collaborators and students say beneath the words and to what experiments tell you beyond your expectations. CommunicationThese early lessons were reinforced in spades during my time at Amherst College as an undergraduate. At the time, Amherst used a core curriculum, so everyone took the same set of classes in the freshman year, and classes drew context from each other. History was focused on Newton's era the same week that Newtonian principles were encountered in physics, and the physics professor proffered his thoughts on how those principles drove history. Learning to write and scrape away a few protective layers to express how you really understood a problem was a pervasive goal in every class, but especially in the venerable English 1 and 2 courses. In those days, it was perfectly acceptable to hold up a trivial attempt at truth by one of us for class ridicule in anticipation of the one glorious day when our composition was read with a modicum of praise. Trial by fire taught us that communication in all forms that conveys what we actually mean lies at the heart of creative advances of all types, including science. I learned many facts in courses at Amherst, nearly all of which have been superseded by the ferocious pace of the advances that have occurred in all fields over recent decades. In contrast, the lessons in critical writing and communication still resonate, and in a real sense, they are the key to any success that I have enjoyed.At Amherst, I was a chemistry major...

show abstract

Oxy Intermediates of Homoprotocatechuate 2,3-Dioxygenase: Facile Electron Transfer between Substrates

Cited by 47 publications

References 42 publications

Oxygen activation in extradiol catecholate dioxygenases – a density functional study

Oxygen activation in extradiol catecholate dioxygenases – a density functional study

Ring-Cleaving Dioxygenases with a Cupin Fold

Life in a Sea of Oxygen

Contact Info

Product

Resources

About