Publications

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

  Yeh H.C., Tsai A.L., Wang L.H.

  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 agg ... >> More

  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 13-hydroxy-14,15-epoxy-5,8,11-eicosatrienoic acid (13-OH-14,15-EET), 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 ( approximately 60 microM 15-HPETE) and TXAS ( approximately 80 microM 15-HPETE), making PGIS a more efficient catalyst for the 15-HPETE reaction. << Less

  Arch. Biochem. Biophys. 461:159-168(2007) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• The lipoxygenase gene ALOXE3 implicated in skin differentiation encodes a hydroperoxide isomerase.

  Yu Z., Schneider C., Boeglin W.E., Marnett L.J., Brash A.R.

  Lipoxygenase (LOX) enzymes form fatty acid hydroperoxides used in membrane remodeling and cell signaling. Mammalian epidermal LOX type 3 (eLOX3) is distinctive in totally lacking this typical oxygenase activity. Surprisingly, genetic evidence has linked mutations in eLOX3 or a colocalizing enzyme, ... >> More

  Lipoxygenase (LOX) enzymes form fatty acid hydroperoxides used in membrane remodeling and cell signaling. Mammalian epidermal LOX type 3 (eLOX3) is distinctive in totally lacking this typical oxygenase activity. Surprisingly, genetic evidence has linked mutations in eLOX3 or a colocalizing enzyme, 12R-LOX, to disruption of the normal permeability barrier of the skin [Jobard, F., Lefèvre, C., Karaduman, A., Blanchet-Bardon, C., Emre, S., Weissenbach, J., Ozgüc, M., Lathrop, M., Prud'homme, J. F. & Fischer, J. (2002) Hum. Mol. Genet. 11, 107-113]. Herein we identify a logical link of the biochemistry to the genetics. eLOX3 functions as a hydroperoxide isomerase (epoxyalcohol synthase) by using the product of 12R-LOX as the preferred substrate. 12R-Hydroperoxyeicosatetraenoic acid (12R-HPETE) is converted to 8R-hydroxy-11R,12R-epoxyeicosa-5Z,9E,14Z-trienoic acid, one of the isomers of hepoxilin A3, and to 12-ketoeicosatetraenoic acid in a 2:1 ratio. Other hydroperoxides, including 8R-HPETE, 12S-HPETE, and 15S-HPETE, as well as the 13S- and 13R-hydroperoxides of linoleic acid are converted less efficiently. Mass spectrometric analysis of the epoxyalcohol formed from [18O]15S-HPETE showed that both hydroperoxy oxygens are retained in the product. We propose that the ferrous form of eLOX3 initiates a redox cycle, unprecedented among LOX in being autocatalytic, in which the hydroperoxy substrate is isomerized to the epoxyalcohol or keto product. Our results provide strong biochemical evidence for a functional linkage of 12R-LOX and eLOX3 and clues into skin biochemistry and the etiology of ichthyosiform diseases in humans. << Less

  Proc. Natl. Acad. Sci. U.S.A. 100:9162-9167(2003) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Human CYP2S1 metabolizes cyclooxygenase- and lipoxygenase-derived eicosanoids.

  Bui P., Imaizumi S., Beedanagari S.R., Reddy S.T., Hankinson O.

  CYP2S1 is a recently described dioxin-inducible cytochrome P450. We previously demonstrated that human CYP2S1 oxidizes a number of carcinogens but only via the peroxide shunt. In this article, we investigated whether human CYP2S1 can metabolize cyclooxygenase- and lipoxygenase-derived lipid peroxi ... >> More

  CYP2S1 is a recently described dioxin-inducible cytochrome P450. We previously demonstrated that human CYP2S1 oxidizes a number of carcinogens but only via the peroxide shunt. In this article, we investigated whether human CYP2S1 can metabolize cyclooxygenase- and lipoxygenase-derived lipid peroxides in a NADPH-independent fashion. Human CYP2S1 metabolizes prostaglandin G(2) (PGG(2)) (K(m) = 0.267 ± 0.072 μM) into several products including 12S-hydroxy-5Z,8E,10E-heptadecatrienoic acid (12-HHT). It also metabolizes prostaglandin H(2) (PGH(2)) (K(m) = 11.7 ± 2.8 μM) into malondialdehyde, 12-HHT, and thromboxane A(2) (TXA(2)). The turnover to 12-HHT by human CYP2S1 (1.59 ± 0.04 min(-1)) is 40-fold higher than that of TXA(2) (0.04 min(-1)). In addition to PGG(2) and PGH(2) metabolism, human CYP2S1 efficiently metabolizes the hydroperoxyeicosatetraenoic acids (5S-, 12S-, and 15S-) and 13S-hydroperoxyoctadecadienoic acid into 5-oxo-eicosatetraenoic acid (turnover = 16.7 ± 0.3 min(-1)), 12-oxo-eicosatetraenoic acid 1 (11.5 ± 0.9 min(-1)), 15-oxo-eicosatetraenoic acid (16.9 ± 0.8 min(-1)), and 13-octadecadienoic acid (20.2 ± 0.9 min(-1)), respectively. Other cytochromes P450 such as CYP1A1, 1A2, 1B1, and 3A4 underwent similar conversions but at slower rates. The fatty acid hydroperoxides were also converted by human CYP2S1 to several epoxyalcohols. Our data indicate that fatty acid endoperoxides and hydroperoxides represent endogenous substrates of CYP2S1 and suggest that the enzyme CYP2S1 may play an important role in the inflammatory process because some of the products that CYP2S1 produces play important roles in inflammation. << Less

  Drug Metab. Dispos. 39:180-190(2011) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.