Hemes and Hemoproteins. 5: Kinetics of the Peroxidatic Activity of Microperoxidase-8: Model for the Peroxidase Enzymes

Baldwin, David A.; Marques, Helder M.; Pratt, J. M.

doi:10.1016/0162-0134(87)80064-8

Journal of Inorganic Biochemistry

1987

DOI: 10.1016/0162-0134(87)80064-8

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Hemes and Hemoproteins. 5: Kinetics of the Peroxidatic Activity of Microperoxidase-8: Model for the Peroxidase Enzymes

David A. Baldwin

Helder M. Marques

J. M. Pratt

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Cited by 111 publications

(76 citation statements)

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“…Various concentrations of 15-HPETE were added to 1 μM of PGIS or TXAS in 1 ml of 20 mM NaPi, pH 7.5, containing 10% glycerol and 1.8 mM guaiacol. The rate of oxidized guaiacol formation was calculated from ΔA 470 /min using Δε 470 = 26.6 mM −1 cm −1 [17]. …”

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Reaction mechanisms of 15-hydroperoxyeicosatetraenoic acid catalyzed by human prostacyclin and thromboxane synthases

Yeh¹,

Tsai²,

Wang³

2007

Archives of Biochemistry and Biophysics

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Prostacyclin synthase (PGIS) and thromboxane synthase (TXAS) are atypical cytochrome P450s. They do not require NADPH or dioxygen for isomerization of prostaglandin H 2 (PGH 2 ) to produce prostacyclin (PGI 2 ) and thromboxane A 2 (TXA 2 ). PGI 2 and TXA 2 have opposing actions on platelet aggregation and blood vessel tone. In this report, we use a lipid hydroperoxide, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), to explore the active site characteristics of PGIS and TXAS. The two enzymes transformed 15-HPETE not only into 8,, like many microsomal P450s, but also to 15-ketoeicosatetraenoic acid (15-KETE) and 15-hydroxyeicosatetraenoic acid (15-HETE). 13-OH-14,15-EET and 15-KETE result from homolytic cleavage of the O-O bond, whereas 15-HETE results from heterolytic cleavage, a common peroxidase pathway. About 80% of 15-HPETE was homolytically cleaved by PGIS and 60% was homolytically cleaved by TXAS. The V max of homolytic cleavage is 3.5-fold faster than heterolytic cleavage for PGIS-catalyzed reactions (1100 min −1 vs. 320 min −1 ) and 1.4-fold faster for TXAS (170 min −1 vs. 120 min −1 ). Similar K M values for homolytic and heterolytic cleavages were found for PGIS (∼60 μM 15-HPETE) and TXAS (∼80 μM 15-HPETE), making PGIS a more efficient catalyst for the 15-HPETE reaction.Keywords prostacyclin synthase; thromboxane synthase; cytochrome P450; peroxide bond cleavage; homolytic; heterolytic; hydroperoxides; epoxyalcohol Prostacyclin synthase (PGIS) and thromboxane synthase (TXAS) are members of the cytochrome P450 superfamily, which uses heme as the prosthetic group and has a cysteine thiolate proximal ligand [1,2]. PGIS and TXAS convert prostaglandin H 2 (PGH 2 ) to prostacyclin (PGI 2 ) and thromboxane A 2 (TXA 2 ), respectively. PGI 2 inhibits platelet activation and aggregation and induces vasodilation, whereas TXA 2 stimulates platelet secretion, aggregation and vasoconstriction [3]. Both PGI 2 and TXA 2 are rapidly hydrolyzed To whom correspondence should be addressed: Lee-Ho Wang Division of Hematology Department of Internal Medicine 6431 Fannin Houston, TX 77030 Tel: 713-500-6794 Fax: 713-500-6810 e-mail: lee-ho.wang@uth.tmc.edu 1 The abbreviations used are: PGIS, prostacyclin synthase; PGI 2 , prostacyclin; PGHS, prostaglandin H synthase; TXAS, thromboxane synthase; TXA 2 , thromboxane A 2 ; 8,11-eicosatrienoic acid; ESI/MS, electron-spray ionization/ mass spectrometry; EPR, electron paramagnetic resonance; SVD, singular value decomposition.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Hecker and Ullrich proposed a caged radical mechanism for TXAS ...

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confidence: 99%

Reaction mechanisms of 15-hydroperoxyeicosatetraenoic acid catalyzed by human prostacyclin and thromboxane synthases

Yeh¹,

Tsai²,

Wang³

2007

Archives of Biochemistry and Biophysics

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“…The reaction of ONOO 2 (or ONOOH) with a variety of biomolecules also results in the production of NO 2 2 [13]. Several heme proteins have been reported to react with NO 2 2 . First, oxyhemoglobin (HbO 2 ) and oxymyoglobin (MbO 2 ) can oxidize NO 2 2 to form methemoglobin and metmyoglobin and NO 3 2 [14].…”

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“…NO X also reacts rapidly with O 2 X2 to yield peroxynitrite (ONOO 2 ) a powerful oxidizing species [12]. The reaction of ONOO 2 (or ONOOH) with a variety of biomolecules also results in the production of NO 2 2 [13]. Several heme proteins have been reported to react with NO 2 2 .…”

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confidence: 99%

“…Nitric oxide (NO X ) plays a key role in both physiological and pathophysiological processes [10]. The autoxidation of NO X with O 2 results in the formation of nitrite NO 2 2 as a primary end product [11]. NO X also reacts rapidly with O 2 X2 to yield peroxynitrite (ONOO 2 ) a powerful oxidizing species [12].…”

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confidence: 99%

“…This weak ligand can be replaced by H 2 O 2 , which allows the formation of highly oxidized intermediates, responsible for two types of catalytic reactions. First of all, MP8 shows a peroxidase-like activity and is able to perform the oxidation of several typical peroxidase cosubstrates like o-dianisine [2], guaiacol [3], 2,2 H -azinobis(3-ethylbenzo-6-thiazolinesulfonic acid) (ABTS) [4]. Second, MP8 also shows a cytochrome P450-like activity and catalyzes the para-hydroxylation of aniline [5], the monooxygenation of polycyclic aromatic compounds [6], the S-oxidation of sulfides [7], and the Nand O-dealkylation of aromatic amines and ethers [8].…”

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confidence: 99%

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Microperoxidase 8 catalyzed nitration of phenol by nitrogen dioxide radicals

Ricoux

Boucher

Mansuy

et al. 2001

European Journal of Biochemistry

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Microperoxidase 8 (MP8) is a heme octapeptide obtained by hydrolytic digestion of horse heart cytochrome c. At pH below 9, the heme iron is axially coordinated to the imidazole side chain of His18 and to a water molecule. Replacement of this weak ligand by H 2 O 2 allows the formation of high-valent iron-oxo species which are responsible for both peroxidase-like and cytochrome P450-like activities of MP8.This paper shows that MP8 is able to catalyze the nitration of phenol by nitrite. The reaction requires H 2 O 2 and is inhibited by ligands having a high affinity for the iron, catalase and radical scavengers. This suggests that the nitrating species could be NO 2 X radicals formed by the oxidation of nitrite by high-valent iron-oxo species.This new activity of MP8 opens a new access to nitroaromatic compounds under mild conditions and validates the use of this minienzyme to mimick heme peroxidases, especially in the reactions of NO-derived species with biomolecules under oxidative stress conditions.

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Effect of the Protein Matrix of Cytochromec in Suppressing the Inherent Peroxidase Activity of Its Heme Prosthetic Group

2002

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Hemes and Hemoproteins. 5: Kinetics of the Peroxidatic Activity of Microperoxidase-8: Model for the Peroxidase Enzymes

Cited by 111 publications

References 29 publications

Reaction mechanisms of 15-hydroperoxyeicosatetraenoic acid catalyzed by human prostacyclin and thromboxane synthases

Reaction mechanisms of 15-hydroperoxyeicosatetraenoic acid catalyzed by human prostacyclin and thromboxane synthases

Microperoxidase 8 catalyzed nitration of phenol by nitrogen dioxide radicals

Effect of the Protein Matrix of Cytochromec in Suppressing the Inherent Peroxidase Activity of Its Heme Prosthetic Group

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