Prostaglandin endoperoxide synthase substituted with manganese protoporphyrin IX. Formation of a higher oxidation state and its relation to cyclooxygenase reaction.

Strieder, Stephan; Schaible, K; Scherer, Hans‐Josef; Dietz, Reiner; Ruf, Hans Heinrich

doi:10.1016/s0021-9258(19)49649-x

Cited by 41 publications

(28 citation statements)

References 30 publications

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“…The rate constant for formation of the oxidized Mn-PGHS peroxidase intermediate upon reaction with 15-HPETE can be roughly estimated to be on the order of 104 M_1 s_l from the data in Figure 5. This is comparable to the value of 4 X 104 M-1 s_1 reported by Strieder et al (1992) for the reaction of Mn-PGHS with 5-phenyl-4-pentenyl hydroperoxide, but about 3 orders of magnitude slower than the rate constant for compound I formation during the reaction of Fe-PGHS with lipid hydroperoxides (Lambeir et al, 1985;Kulmacz, 1986;Dietz et al, 1988;MacDonald et al, 1989). The large difference in peroxidase substrate specificity between Mn-PGHS and Fe-PGHS, with the affinity for lipid hydroperoxides little changed but the affinity for water-soluble hydroperoxides much decreased in Mn-PGHS (see Results), suggests that the metalloporphyrin is a major part of the binding site for water-soluble hydroperoxides but has a smaller influence on the binding of physiological lipid hydroperoxides.…”

Section: Discussionsupporting

confidence: 87%

“…Resting Mn-PGHS exhibited absorbance maxima at 374, 471, and 556 nm, essentially as reported by Strieder et al (1992) and Odenwaller et al (1992). Reaction of Mn-PGHS with EtOOH, 15-HPETE, arachidonate, or 11,14-eicosadienoate resulted in qualitatively the same absorbance changes as those reported by Strieder et al (1992) and Odenwaller et al (1992), with decreases at 374 and 471 nm and the appearance of a new peak at 418 nm. However, different reaction kinetics were observed with individual substrates, as judged from the absorbance changes at 418 nm (Figure 5).…”

Section: Mn-pghssupporting

confidence: 82%

“…As a consequence of the enhanced selectivity of the Mn-PGHS peroxidase for lipid substrates, the use of the small, water-soluble substrates such as HOOH, EtOOH, and 5-phenyl-4-pentenyl hydroperoxide is likely to result in significant underestimation of the peroxidase activity. This may explain the considerably lower estimates of peroxidase activity in Mn-PGHS in earlier reports (Ogino et al, 1978;Thompson & Eling, 1989;Odenwaller et al, 1992;Strieder et al, 1992). The disproportionately slower reactions of the small hydroperoxides with Mn-PGHS may also explain their inability to generate significant amounts of free radical, in contrast to the actions of lipid hydroperoxides (see Results;Lassmann et al, 1991;Strieder et al, 1992).…”

Section: Discussionmentioning

confidence: 82%

“…0006-2960/94/0433-5428$04.50/0 of about 99% of the peroxidase activity (Ogino et al, 1978;Odenwaller et al, 1992;Strieder et al, 1992). These selective perturbations have made the MnPPIX-substituted enzyme (Mn-PGHS) an important experimental subject for elucidation of the details of the cyclooxygenase and peroxidase reaction mechanisms, particularly for testing the proposed role of oxidized peroxidase intermediates and hydroperoxide-induced radicals in cyclooxygenase catalysis.…”

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confidence: 99%

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Reaction and Free Radical Kinetics of Prostaglandin H Synthase with Manganese Protoporphyrin IX as the Prosthetic Group

Kulmacz

Palmer

Wei³

et al. 1994

Biochemistry

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Prostaglandin H synthase (PGHS) is a hemoprotein with both cyclooxygenase and peroxidase activities. Several aspects of the peroxidase and cyclooxygenase activities and the formation of substrate-induced free radical species were characterized with ovine seminal vesicle PGHS reconstituted with manganese protoporphyrin IX (Mn-PGHS) for comparison with the enzyme-containing heme (Fe-PGHS). Compared to Fe-PGHS, the Km of Mn-PGHS peroxidase for ethyl hydroperoxide was much higher, but that for 15-hydroperoxyeicosatetraenoic acid (15-HPETE) was little changed. The Mn-PGHS peroxidase Vmax value with 15-HPETE was about 4% that with Fe-PGHS. Mn-PGHS oxidized 0.95 +/- 0.05 and Fe-PGHS oxidized 2.06 +/- 0.09 mol of TMPD/mol of 15-HPETE. Reaction of 15-HPETE with Mn-PGHS resulted in approximately equal proportions of two lipid products: 15-hydroxyeicosatetraenoic acid (15-HETE) and a compound identified as 15-ketoeicosatetraenoic acid. Fe-PGHS produced only 15-HETE. Thus, 15-HETE can serve as an efficient two-electron reductant of oxidized Mn-PGHS intermediates. The rate of accumulation of oxidized Mn-PGHS intermediate was dependent on the substrate, decreasing in the following order: 15-HPETE > 11,14-eicosadienoate > arachidonate > EtOOH. The cyclooxygenase specific activity increased in a saturable fashion as the concentration of Mn-PGHS was increased, reaching a value higher than that for Fe-PGHS. Computer simulations of the reaction kinetics indicated that this dependence on the Mn-PGHS level was a consequence of the low rate of formation of oxidized peroxidase intermediate. Incubation of Mn-PGHS with either 15-HPETE or arachidonate resulted in the rapid production of a free radical species. The initial accumulation of radical coincided with the synthesis of PGG2 and PGH2, indicating that the radical was kinetically competent to participate in cyclooxygenase catalysis. Reaction with tetranitromethane, a reagent that selectively nitrates tyrosyl residues, destroyed the cyclooxygenase activity of Mn-PGHS, resulting in a much narrower free radical EPR signal. These effects indicate that tyrosine residues are essential for cyclooxygenase activity and that they influence the radical structure in Mn-PGHS.

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Section: Discussionsupporting

confidence: 87%

Section: Mn-pghssupporting

confidence: 82%

Section: Discussionmentioning

confidence: 82%

mentioning

confidence: 99%

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Reaction and Free Radical Kinetics of Prostaglandin H Synthase with Manganese Protoporphyrin IX as the Prosthetic Group

Kulmacz

Palmer

Wei³

et al. 1994

Biochemistry

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“…The abstraction of the 13 -pro-S hydrogen atom from arachidonic acid by a conventional compound I implies that arachidonic acid binds and reacts preferentially with compound I and that ferulic acid reacts preferentially with compound II (Hsuanyu & Dunford, 1992). PGH synthase reconstituted with manganese porphyrin exhibits considerable cyclooxygenase activity but little peroxidase activity (Lassmann et al, 1991;Odenwaller et al, 1992;Strieder et al, 1992). Manganese-substituted yeast cytochrome c peroxidase exhibits properties markedly different from those of the iron holoenzyme, with about 10% of the normal peroxidatic activity (Yonetani & Asakura, 1968).…”

Section: Discussionmentioning

confidence: 99%

Intimate Relation between Cyclooxygenase and Peroxidase Activities of Prostaglandin H Synthase. Peroxidase Reaction of Ferulic Acid and Its Influence on the Reaction of Arachidonic Acid

Bakovic

Dunford²

1994

Biochemistry

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The oxidation of ferulic acid by hydrogen peroxide catalyzed by prostaglandin H synthase follows a modified ping-pong irreversible mechanism, as is the case for classical peroxidases. The rate constant for the reaction of prostaglandin H synthase with hydrogen peroxide, determined from steady-state results, is (1.31 +/- 0.1) x 10(6) M-1 s-1, and for the reaction of prostaglandin H synthase-compound II with ferulic acid it is (5.5 +/- 0.3) x 10(6) M-1 s-1. Cyclooxygenase and peroxidase functions of prostaglandin H synthase were studied by comparing the initial rates of reaction of the cyclooxygenase substrate, arachidonic acid, and a peroxidase reducing substrate, ferulic acid, in mixtures of the two substrates. For both an equimolar ratio of arachidonic and ferulic acids and ferulic acid in excess of arachidonic acid a stimulation of the cyclooxygenase reaction is observed. The concentration of ferulic acid necessary to produce 50% stimulation of 0.2 mM arachidonic acid oxidation is 0.14 +/- 0.02 mM. A striking feature of our results is that prostaglandin H synthase catalyzes oxidation of the two substrates in a constant and fixed molar ratio of ferulic acid to arachidonic acid of 2:1, despite widely different starting concentrations. If arachidonic acid is in excess of ferulic acid, enzyme inactivation occurs. The results can be explained by an interconnected cyclooxygenase-peroxidase unbranched free radical mechanism in which arachidonic acid reacts with either the ferryl oxygen or the porphyrin pi-cation radical part of a conventional peroxidase compound I (a FeIV = O porphyrin pi-cation radical) and ferulic acid reacts with compound II (FeIV = O).(ABSTRACT TRUNCATED AT 250 WORDS)

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The Cyclooxygenases

Malkowski

2017

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Cyclooxygenases (COX‐1 and COX‐2) are membrane‐associated, heme‐containing enzymes that oxygenate arachidonic acid to generate prostaglandin H 2 in the committed step of prostanoid biosynthesis. The resulting prostanoids play a key role in the maintenance of numerous physiological processes within the body. Abnormal changes in COX‐mediated prostanoid production are associated with various disease pathologies, including inflammation, cardiovascular disease, and cancer. Aspirin, nonselective nonsterroidal anti‐inflammatory drugs, and COX‐2‐selective drugs target COX‐1 and COX‐2 to reduce acute and chronic inflammation. As such, the crystal structures of COX‐1 and COX‐2 have been extensively characterized in the presence of substrates and inhibitors in order to gain a deeper understanding at the molecular level of the mechanistic nuances that underlie catalysis and inhibition. This review serves to summarize the recent advances in COX structural biology.

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Prostaglandin endoperoxide synthase substituted with manganese protoporphyrin IX. Formation of a higher oxidation state and its relation to cyclooxygenase reaction.

Cited by 41 publications

References 30 publications

Reaction and Free Radical Kinetics of Prostaglandin H Synthase with Manganese Protoporphyrin IX as the Prosthetic Group

Reaction and Free Radical Kinetics of Prostaglandin H Synthase with Manganese Protoporphyrin IX as the Prosthetic Group

Intimate Relation between Cyclooxygenase and Peroxidase Activities of Prostaglandin H Synthase. Peroxidase Reaction of Ferulic Acid and Its Influence on the Reaction of Arachidonic Acid

The Cyclooxygenases

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