Induction of omega-oxidation of monocarboxylic acids in rats by acetylsalicylic acid.

Dacremont³

et al. 2008

FASEB j.

Very-long-chain fatty acids (VLCFAs) have long been known to be degraded exclusively in peroxisomes via ␤-oxidation. A defect in peroxisomal ␤-oxidation results in elevated levels of VLCFAs and is associated with the most frequent inherited disorder of the central nervous system white matter, X-linked adrenoleukodystrophy. Recently, we demonstrated that VLCFAs can also undergo -oxidation, which may provide an alternative route for the breakdown of VLCFAs. The -oxidation of VLCFA is initiated by CYP4F2 and CYP4F3B, which produce -hydroxy-VLCFAs. In this article, we characterized the enzymes involved in the formation of very-long-chain dicarboxylic acids from -hydroxy-VLCFAs. We demonstrate that very-longchain dicarboxylic acids are produced via two independent pathways. The first is mediated by an as yet unidentified, microsomal NAD ؉ -dependent alcohol dehydrogenase and fatty aldehyde dehydrogenase, which is encoded by the ALDH3A2 gene and is deficient in patients with Sjögren-Larsson syndrome. The second pathway involves the NADPH-dependent hydroxylation of -hydroxy-VLCFAs by CYP4F2, CYP4F3B, or CYP4F3A. Enzyme kinetic studies show that oxidation of -hydroxy-VLCFAs occurs predominantly via the NAD ؉ -dependent route. Overall, our data demonstrate that in humans all enzymes are present for the complete conversion of VLCFAs to their corresponding very-long-chain dicarboxylic acids.-Sanders, R.-J., Ofman, R., Dacremont, G., Wanders, R. J. A., Kemp, S. Characterization of the human -oxidation pathway for -hydroxy-very-long-chain fatty acids. FASEB J. 22,

mentioning

confidence: 99%

Characterization of the human ω‐oxidation pathway for ω‐hydroxy‐very‐long‐chain fatty acids

Dacremont³

et al. 2008

FASEB j.

“…This reaction is carried out by one or more cytochrome P450 enzymes mainly belonging to the CYP4 subfamily and requires NADPH and molecular oxygen (9, 10). Subsequently, the -hydroxy fatty acid may be oxidized further into a -carboxylic acid either via an NAD ϩ -dependent alcohol and aldehyde dehydrogenase system or via a cytochrome P450-mediated route (11)(12)(13)(14). Finally, dicarboxylic acids can be ␤-oxidized in peroxisomes and/or mitochondria to shorter-chain dicarboxylic acids followed by excretion into the urine (15, 16).…”

mentioning

confidence: 99%

ω-Oxidation of Very Long-chain Fatty Acids in Human Liver Microsomes

Journal of Biological Chemistry

Durán

et al. 2006

X-linked adrenoleukodystrophy (X-ALD) is a severe neurodegenerative disorder biochemically characterized by elevated levels of very long-chain fatty acids (VLCFA). Excess levels of VLCFAs are thought to play an important role in the pathogenesis of X-ALD. Therefore, therapeutic approaches for X-ALD are focused on the reduction or normalization of VLCFAs. In this study, we investigated an alternative oxidation route for VLCFAs, namely -oxidation. The results described in this study show that VLCFAs are substrates for the -oxidation system in human liver microsomes. Moreover, VLCFAs were not only converted into -hydroxy fatty acids, but they were also further oxidized to dicarboxylic acids via cytochrome P450-mediated reactions. High sensitivity toward the specific P450 inhibitor 17-octadecynoic acid suggested that -hydroxylation of VLCFAs is catalyzed by P450 enzymes belonging to the CYP4A/F subfamilies. Studies with individually expressed human recombinant P450 enzymes revealed that two P450 enzymes, i.e. CYP4F2 and CYP4F3B, participate in the -hydroxylation of VLCFAs. Both enzymes belong to the cytochrome P450 4F subfamily and have a high affinity for VLCFAs. In summary, this study demonstrates that VLCFAs are substrates for the human -oxidation system, and for this reason, stimulation of the in vivo VLCFA -oxidation pathway may provide an alternative mode of treatment to reduce the levels of VLCFAs in patients with X-ALD.In mammalian cells, fatty acid oxidation plays a major role in the production of energy, particularly in the heart and skeletal muscle, and is the main energy source during periods of fasting. Both mitochondria and peroxisomes are capable of degrading saturated fatty acids via ␤-oxidation. Short-, medium-, and long-chain saturated fatty acids are degraded predominantly by mitochondria, whereas very long-chain fatty acids (VLCFA, 2 Ͼ22 carbons) are ␤-oxidized exclusively in peroxisomes (1, 2). Moreover, peroxisomes also metabolize certain branched chain fatty acids, bile acid precursors, eicosanoids, and dicarboxylic acids (3).X-linked adrenoleukodystrophy (X-ALD: MIM 300100), the most common peroxisomal disorder, is a progressive neurodegenerative disease that affects the cerebral white matter, spinal cord, peripheral nerves, adrenal cortex, and testis (4). X-ALD is caused by mutations in the ABCD1 gene that encodes ALDP, an ATP-binding cassette transporter located in the peroxisomal membrane with an unknown function (5). Biochemically, X-ALD is characterized by elevated levels of saturated and monounsaturated VLCFAs in plasma and tissues due to the impaired ␤-oxidation of VLCFAs in peroxisomes (6 -8). Since the pathogenesis of X-ALD is probably due to the increased levels of VLCFAs, correction of VLCFA levels is one of the primary objectives in therapeutic approaches. These include gene replacement therapy, bone marrow transplantation, lovastatin treatment, inhibition of VLCFA biosynthesis by mono-unsaturated fatty acids, notably oleic acid (C18:19) and erucic acid (C22:19) (Lorenzo's oil), a...

“…Finally, this product can be converted into a dicarboxylic acid by an aldehyde dehydrogenase. Dehydrogenation of -hydroxy-and -oxo-fatty acids requires NAD ϩ and has been identified in the cytosol (5,9,10). The dicarboxylic acids that are produced via the -oxidation pathway can be either excreted into the urine or ␤ -oxidized in mitochondria or peroxisomes (11)(12)(13).…”

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confidence: 99%

Evidence for two enzymatic pathways for ω-oxidation of docosanoic acid in rat liver microsomes

Journal of Lipid Research

Valianpour

et al. 2005

We studied the -oxidation of docosanoic acid (C22:0) in rat liver microsomes. C22:0 and 22-hydroxydocosanoic acid ( -hydroxy-C22:0) were used as substrates, and the reaction products were analyzed by electrospray ionization mass spectrometry. In the presence of NADPH, -oxidation of C22:0 produced not only the hydroxylated product, -hydroxy-C22:0, but also the dicarboxylic acid of C22:0, docosanedioic acid (C22:0-DCA). When rat liver microsomes were incubated with -hydroxy-C22:0 in the presence of either NAD ؉ or NADPH, C22:0-DCA was formed readily. Formation of C22:0-DCA from either C22:0 or -hydroxy-C22:0 with NADPH as cofactor was inhibited strongly by miconazole and disulfiram, whereas no inhibition was found with NAD ؉ as cofactor. Furthermore, -oxidation of C22:0 was reduced significantly when molecular oxygen was depleted. The high sensitivity toward the more specific cytochrome P450 inhibitors ketoconazole and 17-octadecynoic acid suggests that hydroxylation of C22:0 and -hydroxy-C22:0 may be catalyzed by one or more cytochrome P450 hydroxylases belonging to the CYP4A and/or CYP4F subfamily. This study demonstrates that C22:0 is a substrate for the -oxidation system in rat liver microsomes and that the product of the first hydroxylation step, -hydroxy-C22:0, may undergo further oxidation via two distinct pathways driven by NAD ؉ or NADPH. -Sanders, R-J., R. Ofman, F. Valianpour, S. Kemp, and R. J. A. Wanders. Evidence for two enzymatic pathways for -oxidation of docosanoic acid in rat liver microsomes. J. Lipid Res. 2005. 46: 1001-1008.