Tyrosyl radicals and their role in hydroperoxide-dependent activation and inactivation of prostaglandin endoperoxide synthase

Smith, William L.; Eling, Thomas E.; Kulmacz, Richard J.; Marnett, Lawrence J.; Tsai, Alan C.

doi:10.1021/bi00116a001

Cited by 134 publications

(84 citation statements)

References 50 publications

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“…Furthermore, recent works have demonstrated that the addition of hydrogen peroxide to the fully oxidized CcO can result in formation of the same compound P and compound F species (44 -46). The tyrosyl radical is known to have a role in the electron transfer events in Photosystem II (47,48), prostaglandin synthase (49,50), and ribonucleotide reductase (51). Circumstantial evidence suggests that the participation of the tyrosyl radical in the enzyme turn-over of CcO is possible (24).…”

Section: Discussionmentioning

confidence: 99%

An Electron Spin Resonance Spin-trapping Investigation of the Free Radicals Formed by the Reaction of Mitochondrial Cytochromec Oxidase with H2O2

Chen

Gunther

Mason

1999

Journal of Biological Chemistry

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The reaction of purified bovine mitochondrial cytochrome c oxidase (CcO) and hydrogen peroxide was studied using the ESR spin-trapping technique. A protein-centered radical adduct was trapped by 5,5-dimethyl-1-pyrroline N-oxide and was assigned to a thiyl radical adduct based on its hyperfine coupling constants of a N ‫؍‬ 14.7 G and a ␤ H ‫؍‬ 15.7 G. The ESR spectra obtained using the nitroso spin traps 3,5-dibromo-4-nitrosobenzenesulfonic acid (

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Section: Discussionmentioning

confidence: 99%

An Electron Spin Resonance Spin-trapping Investigation of the Free Radicals Formed by the Reaction of Mitochondrial Cytochromec Oxidase with H2O2

Chen

Gunther

Mason

1999

Journal of Biological Chemistry

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“…The tyrosyl radical produced removes hydrogen from the substrate. 35 In the absence of substrate or inhibitor, Tyr385 forms a hydrogen bond with a water molecule which connects Tyr385 with Ser530 thus stabilising the molecule. The position of Tyr385 within an extremely hydrophobic neighbourhood makes any electrostatic interaction or hydrogen bond formation of great importance.…”

Section: Docking Resultsmentioning

confidence: 99%

N-substituted [phenyl-pyrazolo]-oxazin-2-thiones as COX-LOX inhibitors: influence of the replacement of the oxo -group with thioxo- group on the COX inhibition activity of N-substituted pyrazolo-oxazin-2-ones

Geronikaki¹,

Bennamane²,

Nedjar-Kolli³

et al. 2010

Arkivoc

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Targeting to the synthesis of potent dual acting COX/LOX inhibitors as future anti-inflammatory drugs, we attempted a modification of the compounds based on docking analysis results. A substitution of the oxygen of the oxo-group of the oxazin-2-one ring by sulphur resulted in a four to over ten fold improvement of COX and LOX inhibitory action. N-phenyl derivatives exhibited the best biological properties with the 4-methoxy-phenyl derivative showing the best COX-1 and LOX inhibitory action and the 4-Br-phenyl derivative exhibiting the best COX-2 inhibitory action combined with good COX-1 and LOX inhibitory capacity.

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“…First, the separate measurements of peroxidase and cyclooxygenase active site stability produce convergent values. The cyclooxygenase activity of both PGHS isoforms requires initiation via peroxidase intermediates (17,44,54). Because of this mechanistic linkage, disruption of the peroxidase site would be expected to lead to indirect loss of peroxidase activity.…”

Section: Discussionmentioning

confidence: 99%

Comparison of Structural Stabilities of Prostaglandin H Synthase-1 and -2

Xiao

Chen

Kulmacz

1998

Journal of Biological Chemistry

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There are two known isoforms of prostaglandin H synthase (PGHS), a key enzyme in the conversion of arachidonic acid to bioactive prostanoids. The "constitutive" isoform, PGHS-1, is thought to have housekeeping functions, and the "inducible" isoform, PGHS-2, has been implicated in cellular responses to cytokines. The two isoforms have high sequence conservation in the cyclooxygenase active site and quite similar crystallographic structures, but differ markedly in their interactions with many cyclooxygenase substrates and inhibitors. We have evaluated the stability of the overall folding, and of the active sites of ovine PGHS-1 and human PGHS-2 using denaturation with guanidinium hydrochloride (GdmHCl). Changes in hydrodynamic and cross-linking properties indicated a dimer 3 monomer transition for both isoforms between 0.5 and 2 M GdmHCl; the monomers unfolded at higher GdmHCl levels. Changes in overall secondary and tertiary structure, measured by tryptophan fluorescence and circular dichroism, occurred in two phases for each isoform, with the transition between the phases at 0.2-0.5 M GdmHCl. Disruption of active site functions (cyclooxygenase, peroxidase, and cyclooxygenase inhibitor binding activities) began at GdmHCl levels below 0.2 M. The structural and functional changes were completely reversible up to about 2 M GdmHCl, they were more pronounced at lower protein levels, and they required lower GdmHCl levels for PGHS-2 than for PGHS-1. The results are consistent with a four-state denaturation process for both isoforms: native dimers 3 inactive dimers 3 compact monomers 3 unfolded monomers. The first two steps are reversible for both isoforms; PGHS-2 undergoes the first and last steps more readily than PGHS-1. Thus, the structural stability of PGHS-2, both in the active site regions and in the subunits overall, is distinctly less than that of PGHS-1. These differences in structural stability may contribute to the isoforms' active site ligand selectivity. Prostaglandin H synthase (PGHS)1 catalyzes two key steps in prostanoid biosynthesis: oxygenation and cyclization of arachidonic to form PGG 2 and the reduction of the hydroperoxide of PGG 2 to form PGH 2 . Two isoforms of PGHS have been described. PGHS-1 is believed to be a housekeeping enzyme, whereas PGHS-2 is thought to play important roles in cell proliferation and inflammation (1). Both isoforms have cyclooxygenase and peroxidase activity, with comparable specific activities for the purified recombinant enzymes (2). PGHS-1 and PGHS-2 have about 60% amino acid identity, with much higher conservation of active site residues (3). Crystallographic data for oPGHS-1 and hPGHS-2 revealed similar dimeric structures for the two isoforms, with a root-mean-square deviation of only 0.9 Å for backbone atoms (4 -6).Despite the similarities in the crystallographic structures, the two PGHS isoforms have been found to have different selectivities for fatty acid substrates and cyclooxygenase inhibitors (1). These specificities have been ascribed in part to a larger cycl...

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Tyrosyl radicals and their role in hydroperoxide-dependent activation and inactivation of prostaglandin endoperoxide synthase

Cited by 134 publications

References 50 publications

An Electron Spin Resonance Spin-trapping Investigation of the Free Radicals Formed by the Reaction of Mitochondrial Cytochromec Oxidase with H2O2

An Electron Spin Resonance Spin-trapping Investigation of the Free Radicals Formed by the Reaction of Mitochondrial Cytochromec Oxidase with H2O2

N-substituted [phenyl-pyrazolo]-oxazin-2-thiones as COX-LOX inhibitors: influence of the replacement of the oxo -group with thioxo- group on the COX inhibition activity of N-substituted pyrazolo-oxazin-2-ones

Comparison of Structural Stabilities of Prostaglandin H Synthase-1 and -2

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