(Below N is a link to NCBI taxonomic web page and E link to ESTHER at designed phylum.) > cellular organisms: NE > Eukaryota: NE > Opisthokonta: NE > Metazoa: NE > Eumetazoa: NE > Bilateria: NE > Deuterostomia: NE > Chordata: NE > Craniata: NE > Vertebrata: NE > Gnathostomata: NE > Teleostomi: NE > Euteleostomi: NE > Sarcopterygii: NE > Dipnotetrapodomorpha: NE > Tetrapoda: NE > Amniota: NE > Mammalia: NE > Theria: NE > Eutheria: NE > Boreoeutheria: NE > Euarchontoglires: NE > Primates: NE > Haplorrhini: NE > Simiiformes: NE > Catarrhini: NE > Hominoidea: NE > Hominidae: NE > Homininae: NE > Homo: NE > Homo sapiens: NE
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MPELVVTALLAPSRLSLKLLRAFMWSLVFSVALVAAAVYGCIALTHVLCR PRRGCCGRRRSASPACLSDPSLGEHGFLNLKSSGLRLHYVSAGRGNGPLM LFLHGFPENWFSWRYQLREFQSRFHVVAVDLRGYGPSDAPRDVDCYTIDL LLVDIKDVILGLGYSKCILVAHDWGALLAWHFSIYYPSLVERMVVVSGAP MSVYQDYSLHHISQFFRSHYMFLFQLPWLPEKLLSMSDFQILKTTLTHRK TGIPCLTPSELEAFLYNFSQPGGLTGPLNYYRNLFRNFPLEPQELTTPTL LLWGEKDTYLELGLVEAIGSRFVPGRLEAHILPGIGHWIPQSNPQEMHQY MWAFLQDLLD
The mammalian epoxide hydrolase (EPHX)3 is known from in vitro experiments to efficiently hydrolyze the linoleate epoxides 9,10-epoxyoctadecamonoenoic acid (EpOME) and epoxyalcohol 9R,10R-trans-epoxy-11E-13R-hydroxy-octadecenoate to corresponding diols and triols, respectively. Herein we examined the physiological relevance of EPHX3 to hydrolysis of both substrates in vivo. Ephx3(-)(/)(-) mice show no deficiency in EpOME-derived plasma diols, discounting a role for EPHX3 in their formation, whereas epoxyalcohol-derived triols esterified in acylceramides of the epidermal 12R-lipoxygenase pathway are reduced. Although the Ephx3(-)(/)(-) pups appear normal, measurements of transepidermal water loss detected a modest and statistically significant increase compared with the wild-type or heterozygote mice, reflecting a skin barrier impairment that was not evident in the knockouts of mouse microsomal (EPHX1/microsomal epoxide hydrolase) or soluble (EPHX2/sEH). This barrier phenotype in the Ephx3(-)(/)(-) pups was associated with a significant decrease in the covalently bound ceramides in the epidermis (40% reduction, p < 0.05), indicating a corresponding structural impairment in the integrity of the water barrier. Quantitative LC-MS analysis of the esterified linoleate-derived triols in the murine epidermis revealed a marked and isomer-specific reduction (-85%) in the Ephx3(-)(/)(-) epidermis of the major trihydroxy isomer 9R,10S,13R-trihydroxy-11E-octadecenoate. We conclude that EPHX3 (and not EPHX1 or EPHX2) catalyzes hydrolysis of the 12R-LOX/eLOX3-derived epoxyalcohol esterified in acylceramide and may function to control flux through the alternative and crucial route of metabolism via the dehydrogenation pathway of SDR9C7. Importantly, our findings also identify a functional role for EPHX3 in transformation of a naturally esterified epoxide substrate, pointing to its potential contribution in other tissues.
Title: The Precise Structures and Stereochemistry of Trihydroxy-linoleates Esterified in Human and Porcine Epidermis and Their Significance in Skin Barrier Function: implication of an epoxide hydrolase in the transformation of linoleate Chiba T, Thomas CP, Calcutt MW, Boeglin WE, O'Donnell VB, Brash AR Ref: Journal of Biological Chemistry, 291:14540, 2016 : PubMed
Creation of an intact skin water barrier, a prerequisite for life on dry land, requires the lipoxygenase-catalyzed oxidation of the essential fatty acid linoleate, which is esterified to the omega-hydroxyl of an epidermis-specific ceramide. Oxidation of the linoleate moiety by lipoxygenases is proposed to facilitate enzymatic cleavage of the ester bond, releasing free omega-hydroxyceramide for covalent binding to protein, thus forming the corneocyte lipid envelope, a key component of the epidermal barrier. Herein, we report the transformations of esterified linoleate proceed beyond the initial steps of oxidation and epoxyalcohol synthesis catalyzed by the consecutive actions of 12R-LOX and epidermal LOX3. The major end product in human and porcine epidermis is a trihydroxy derivative, formed with a specificity that implicates participation of an epoxide hydrolase in converting epoxyalcohol to triol. Of the 16 possible triols arising from hydrolysis of 9,10-epoxy-13-hydroxy-octadecenoates, using LC-MS and chiral analyses, we identify and quantify specifically 9R,10S,13R-trihydroxy-11E-octadecenoate as the single major triol esterified in porcine epidermis and the same isomer with lesser amounts of its 10R diastereomer in human epidermis. The 9R,10S,13R-triol is formed by SN2 hydrolysis of the 9R,10R-epoxy-13R-hydroxy-octadecenoate product of the LOX enzymes, a reaction specificity characteristic of epoxide hydrolase. The high polarity of triol over the primary linoleate products enhances the concept that the oxidations disrupt corneocyte membrane lipids, promoting release of free omega-hydroxyceramide for covalent binding to protein and sealing of the waterproof barrier.
Epoxide hydrolases are a small superfamily of enzymes important for the detoxification of chemically reactive xenobiotic epoxides and for the processing of endogenous epoxides that act as signaling molecules. Here, we report the identification of two human epoxide hydrolases: EH3 and EH4. They share 45% sequence identity, thus representing a new family of mammalian epoxide hydrolases. Quantitative RT-PCR from mouse tissue indicates strongest EH3 expression in lung, skin, and upper gastrointestinal tract. The recombinant enzyme shows a high turnover number with 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid (EET), as well as 9,10-epoxyoctadec-11-enoic acid (leukotoxin). It is inhibited by a subclass of N,N'-disubstituted urea derivatives, including 12-(3-adamantan-1-yl-ureido)-dodecanoic acid, 1-cyclohexyl-3-dodecylurea, and 1-(1-acetylpiperidin-4-yl)-3-(4-(trifluoromethoxy)phenyl)urea, compounds so far believed to be selective inhibitors of mammalian soluble epoxide hydrolase (sEH). Its sensitivity to this subset of sEH inhibitors may have implications on the pharmacologic profile of these compounds. This is particularly relevant because sEH is a potential drug target, and clinical trials are under way exploring the value of sEH inhibitors in the treatment of hypertension and diabetes type II.
Homo sapiens (Human) esterase D (EC 3.1.1.1) formylglutathione hydrolase