CYP4 Isoenzyme Specificity and the Relationship between .omega.-Hydroxylation and Terminal Desaturation of Valproic Acid

Rettie, Allan E.; Sheffels, Pamela; Korzekwa, Kenneth R.; Gonzalez, Frank J.; Philpot, Richard M.; Baillie, Thomas A.

doi:10.1021/bi00024a013

Cited by 81 publications

(60 citation statements)

References 27 publications

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“…Here we provide evidence for direct activation of the terminal methyl carbon and subsequent formation of -hydroxylated alcohols, a process that appears to be inversely related to the predicted stability of the rearranged product (i.e., straight-chain analogs form greater amounts of -hydroxylated products than do saturated capsaicinoids and capsaicinoids with a tertiary allylic motif, due, presumably, to lower propensities for rearrangement to secondary carbocations that are not highly stabilized, like the tertiary allylic carbocation of capsaicin). Deuterium isotope effects in the formation of 5-hydroxy valproic acid by CYP4B1 (Rettie et al, 1995) and the formation of 20-hydroxyeicosatetraenoic acid by 4F2 and 4A11 (Powell et al, 1998) also support the concept of sterically controlled terminal hydrogen abstraction.…”

Section: Discussionmentioning

confidence: 96%

Structural and Enzymatic Parameters That Determine Alkyl Dehydrogenation/Hydroxylation of Capsaicinoids by Cytochrome P450 Enzymes

Reilly

Yost²

2005

Drug Metab Dispos

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ABSTRACT:Previous studies on the metabolism of capsaicinoids, natural products isolated from chili peppers, demonstrated the production of unique macrocyclic, alkyl dehydrogenated, -, and -1-hydroxylated products. This study investigated the structural and enzymatic parameters that direct selective alkyl dehydrogenation and hydroxylation of capsaicinoids, using a variety of structurally related capsaicinoid analogs and cytochrome P450 (P450) enzymes. CYP2C9 preferentially catalyzed alkyl dehydrogenation, whereas CYP2E1 and 3A4 catalyzed -and -1-hydroxylation, respectively. Analysis of incubations containing various P450s and structural variants of capsaicin by liquid chromatography-tandem mass spectrometry demonstrated similarities in the rate of capsaicinoid metabolism, but marked differences in the metabolite profiles. Production of macrocyclic and -1-hydroxylated metabolites from the various capsaicinoids was dependent on the structure of the alkyl terminus and P450 enzyme. A tertiary carbon at the -1 position, coupled to an adjacent unsaturated bond at the -2,3 position, enhanced the formation of the macrocyclic and dehydrogenated metabolites and were requisite structural features for -1-hydroxylated product formation. Conversely, substrates lacking these structural features were efficiently oxidized to thehydroxylated metabolite. These data were consistent with our hypothesis that metabolism of the alkyl portion of capsaicinoids was governed, in part, by the stability and propensity to form an intermediate radical and a carbocation, and a direct interaction between the alkyl terminus and the heme of many P450 enzymes. These results provided valuable insights into potential mechanisms by which P450s metabolize capsaicinoids and highlight critical chemical features that may also govern the metabolism of structurally related compounds including fatty acids, monoterpenes, and isoprenoids.The capsaicinoids are a family of natural products isolated from the dried fruits of chili peppers (Capsicum annum and Capsicum frutescens) (Govindarajan, 1985;Govindarajan and Sathyanarayana, 1991;Caterina et al., 1997). These substances are the principals that produce the characteristic sensations associated with the ingestion of spicy cuisine as well as the agents responsible for causing severe irritation, inflammation, erythema, and transient hyper-and hypoalgesia at sites exposed to capsaicinoids; capsaicinoids are particularly irritating to the eyes, skin, nose, tongue, and respiratory tract. There are six naturally occurring capsaicinoid analogs: capsaicin, dihydrocapsaicin, nordihydrocapsaicin, nonivamide, homocapsaicin, and homodihydrocapsaicin ( Fig. 1) (Reilly et al., 2001). All capsaicinoid analogs possess a 3-hydroxy-4-methoxy-benzylamide (vanilloid ring) pharmacophore, but differ from capsaicin in their hydrophobic alkyl side chain. Differences in the side chain moiety include saturation of C 15-16 (the -2,3 position), deletion of a methyl group at C 17 (loss of the tertiary carbon), and changes in the length of t...

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Section: Discussionmentioning

confidence: 96%

Structural and Enzymatic Parameters That Determine Alkyl Dehydrogenation/Hydroxylation of Capsaicinoids by Cytochrome P450 Enzymes

Reilly

Yost²

2005

Drug Metab Dispos

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“…We had argued before that the appearance of epoxyalcohols in association with allene oxide synthesis by a purified CYP74 enzyme is evidence of a close parallel in the mechanism of their production (60). (A parallel can be made with conventional P450s, which typically hydroxylate their substrate yet a few can also catalyze desaturation (62)(63)(64)(65)(66)(67).) The fatty acid epoxyalcohols were produced previously when flaxseed AOS (CYP74A1) was presented with unnatural hydroxy-hydroperoxy fatty acid substrates (60).…”

Section: Discussionmentioning

confidence: 99%

Evidence for an Ionic Intermediate in the Transformation of Fatty Acid Hydroperoxide by a Catalase-related Allene Oxide Synthase from the Cyanobacterium Acaryochloris marina

Gao

Boeglin

Zheng

et al. 2009

Journal of Biological Chemistry

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Allene oxides are reactive epoxides biosynthesized from fatty acid hydroperoxides by specialized cytochrome P450s or by catalase-related hemoproteins. Here we cloned, expressed, and characterized a gene encoding a lipoxygenase-catalase/peroxidase fusion protein from Acaryochloris marina. We identified novel allene oxide synthase (AOS) activity and a by-product that provides evidence of the reaction mechanism. The fatty acids 18.43 and 18.33 are oxygenated to the 12R-hydroperoxide by the lipoxygenase domain and converted to the corresponding 12R,13-epoxy allene oxide by the catalase-related domain. Linoleic acid is oxygenated to its 9R-hydroperoxide and then, surprisingly, converted ϳ70% to an epoxyalcohol identified spectroscopically and by chemical synthesis as 9R,10S-epoxy-13S-hydroxyoctadeca-11E-enoic acid and only ϳ30% to the 9R,10-epoxy allene oxide. Experiments using oxygen-18-labeled 9R-hydroperoxide substrate and enzyme incubations conducted in H A diverse spectrum of signaling molecules is biosynthesized in nature from polyunsaturated fatty acids, their peroxides, and further transformations of the fatty acid peroxides. The peroxides are formed by two classes of dioxygenase enzyme. The hemoprotein dioxygenases include prostaglandin H synthase (cyclooxygenase) in animals (1), ␣-dioxygenase in plants (2), and several linoleate dioxygenases in fungi (3-5). The nonheme iron lipoxygenases are even more widespread, being almost ubiquitous among organisms that contain polyunsaturated fatty acids (6 -8). Although further biosynthetic transformation is sometimes accomplished by an additional catalytic activity of the initiating dioxygenase (e.g. leukotriene A 4 synthase (9) or aldehyde-synthesizing hydroperoxide cleaving activity (10) among the LOX 2 enzymes), commonly another distinct enzyme is used to rearrange or otherwise modify the reactive fatty acid peroxide intermediate. Two hemoprotein types are found that have become specialized for this biosynthetic role: cytochrome P450s and catalase-related enzymes.The fatty acid peroxide-metabolizing P450s are by far the better known and include CYP5 (thromboxane synthase) and CYP8A (prostacyclin synthase) in animals (11), and the entire family of CYP74 in plants (12). The individual CYP74 enzymes include allene oxide synthase (AOS), one of which catalyzes a key step in cyclopentenone synthesis in the jasmonate pathway, hydroperoxide lyase, divinyl ether synthase, and epoxyalcohol synthase (12, 13). The catalase-related enzymes are distinctive in that they have been found naturally as a fusion protein with the LOX enzyme that forms their hydroperoxide substrate (14). The known activities include AOS in Plexaura homomalla and other marine corals (with a different specificity for fatty acid hydroperoxide compared with the plant P450 AOS) (15,16), and the unique bicyclobutane synthase and other allylic epoxide synthase activities of the enzyme in the cyanobacterium Anabaena 18). Currently we are trying to understand the scope of the reactions catalyzed by this catala...

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“…This goes along with our identification of multiple isomers of both 1-deoxySO-OH and 1-deoxySA-2OH. Furthermore, although the main function of CYP enzymes is hydroxylation, they can also act as desaturases (54), which might explain the formation of the 1-deoxySAdiene metabolites.…”

Section: The Downstream Metabolism Of 1-deoxyso Is Mediated By Cyp4f mentioning

confidence: 99%

Cytotoxic 1-deoxysphingolipids are metabolized by a cytochrome P450-dependent pathway

Alecu¹,

Othman²,

Penno³

et al. 2017

Journal of Lipid Research

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This article is available online at http://www.jlr.org Sphingolipid (SL) de novo synthesis typically starts with the condensation of serine and palmitoyl-CoA, a reaction catalyzed by serine palmitoyltransferase (SPT) (1-3). SPT can also use alanine in certain conditions (4), which results in the formation of the atypical cytotoxic 1-deoxysphingolipids (1-deoxySLs). These lack the C1-hydroxyl group of regular SLs, which is essential for further metabolic steps and degradation (4, 5). As such, 1-deoxySLs are commonly believed to be "dead-end" metabolites that accumulate within cells, tissues, and body fluids.Pathologically elevated 1-deoxySLs have been found in a number of neurological and metabolic disorders. They are a hallmark of hereditary sensory autonomic neuropathy type 1 (HSAN1), a rare autosomal dominant inherited peripheral neuropathy that is caused by various mutations in SPT. Plasma 1-deoxySLs are also elevated in patients with nondiabetic metabolic syndrome (MetS) and T2D (6) and may contribute to the development of diabetic sensory polyneuropathy (DSN), which is clinically very similar to HSAN1 (7,8). Both conditions start in the lower extremities with a loss of sensation often accompanied by positive sensory symptoms such as hyperpathia and neuropathic pain, as well as the development of painless wounds leading to ulcers (9, 10). L-serine supplementation was shown to effectively lower 1-deoxySL levels while improving Abstract The 1-deoxysphingolipids (1-deoxySLs) are atypical sphingolipids (SLs) that are formed when serine palmitoyltransferase condenses palmitoyl-CoA with alanine instead of serine during SL synthesis. The 1-deoxySLs are toxic to neurons and pancreatic -cells. Pathologically elevated 1-deoxySLs cause the inherited neuropathy, hereditary sensory autonomic neuropathy type 1 (HSAN1), and are also found in T2D. Diabetic sensory polyneuropathy (DSN) and HSAN1 are clinically very similar, suggesting that 1-deoxySLs may be implicated in both pathologies. The 1-deoxySLs are considered to be dead-end metabolites, as they lack the C1-hydroxyl group, which is essential for the canonical degradation of SLs. Here, we report a previously unknown metabolic pathway, which is capable of degrading 1-deoxySLs. Using a variety of metabolic labeling approaches and high-resolution high-accuracy MS, we identified eight 1-deoxySL downstream metabolites, which appear to be formed by cytochrome P450 (CYP)4F enzymes. Comprehensive inhibition and induction of CYP4F enzymes blocked and stimulated, respectively, the formation of the downstream metabolites. Consequently, CYP4F enzymes might be novel therapeutic targets for the treatment of HSAN1 and DSN, as well as for the prevention of T2D. (I.A., A.O., T.H., and A.v.E.) Abbreviations: ATRA, all-trans retinoic acid; CYP, cytochrome P450; DB, double bond; 1-deoxySA, 1-deoxysphinganine; 1-deoxySAdiene, deoxysphingadiene; 1-deoxySA-OH, hydroxyl-deoxysphinganine; 1-deoxySA-2OH, dihydroxyl-deoxysphinganine; 1-deoxySL, 1-deoxysphingolipid; 1-deoxySO, 1-deoxysphingosi...

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CYP4 Isoenzyme Specificity and the Relationship between .omega.-Hydroxylation and Terminal Desaturation of Valproic Acid

Cited by 81 publications

References 27 publications

Structural and Enzymatic Parameters That Determine Alkyl Dehydrogenation/Hydroxylation of Capsaicinoids by Cytochrome P450 Enzymes

Structural and Enzymatic Parameters That Determine Alkyl Dehydrogenation/Hydroxylation of Capsaicinoids by Cytochrome P450 Enzymes

Evidence for an Ionic Intermediate in the Transformation of Fatty Acid Hydroperoxide by a Catalase-related Allene Oxide Synthase from the Cyanobacterium Acaryochloris marina

Cytotoxic 1-deoxysphingolipids are metabolized by a cytochrome P450-dependent pathway

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