Publications

• The human FA2H gene encodes a fatty acid 2-hydroxylase.

  Alderson N.L., Rembiesa B.M., Walla M.D., Bielawska A., Bielawski J., Hama H.

  2-Hydroxysphingolipids are a subset of sphingolipids containing 2-hydroxy fatty acids. The 2-hydroxylation occurs during de novo ceramide synthesis and is catalyzed by fatty acid 2-hydroxylase (also known as fatty acid alpha-hydroxylase). In mammals, 2-hydroxysphingolipids are present abundantly i ... >> More

  2-Hydroxysphingolipids are a subset of sphingolipids containing 2-hydroxy fatty acids. The 2-hydroxylation occurs during de novo ceramide synthesis and is catalyzed by fatty acid 2-hydroxylase (also known as fatty acid alpha-hydroxylase). In mammals, 2-hydroxysphingolipids are present abundantly in brain because the major myelin lipids galactosylceramides and sulfatides contain 2-hydroxy fatty acids. Here we report identification and characterization of a human gene that encodes a fatty acid 2-hydroxylase. Data base searches revealed a human homologue of the yeast ceramide 2-hydroxylase gene (FAH1), which we named FA2H. The FA2H gene encodes a 372-amino acid protein with 36% identity and 46% similarity to yeast Fah1p. The amino acid sequence indicates that FA2H protein contains an N-terminal cytochrome b5 domain and four potential transmembrane domains. FA2H also contains the iron-binding histidine motif conserved among membrane-bound desaturases/hydroxylases. COS7 cells expressing human FA2H contained 3-20-fold higher levels of 2-hydroxyceramides (C16, C18, C24, and C24:1) and 2-hydroxy fatty acids compared with control cells. Microsomal fractions prepared from transfected COS7 cells showed tetracosanoic acid 2-hydroxylase activities in an NADPH- and NADPH: cytochrome P-450 reductase-dependent manner. FA2H lacking the N-terminal cytochrome b5 domain had little activity, indicating that this domain is a functional component of this enzyme. Northern blot analysis showed that the FA2H gene is highly expressed in brain and colon tissues. These results demonstrate that the human FA2H gene encodes a fatty acid 2-hydroxylase. FA2H is likely involved in the formation of myelin 2-hydroxy galactosylceramides and -sulfatides. << Less

  J. Biol. Chem. 279:48562-48568(2004) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• A mammalian fatty acid hydroxylase responsible for the formation of alpha-hydroxylated galactosylceramide in myelin.

  Eckhardt M., Yaghootfam A., Fewou S.N., Zoeller I., Gieselmann V.

  Hydroxylation is an abundant modification of the ceramides in brain, skin, intestinal tract and kidney. Hydroxylation occurs at the sphingosine base at C-4 or within the amide-linked fatty acid. In myelin, hydroxylation of ceramide is exclusively found at the alpha-C atom of the fatty acid moiety. ... >> More

  Hydroxylation is an abundant modification of the ceramides in brain, skin, intestinal tract and kidney. Hydroxylation occurs at the sphingosine base at C-4 or within the amide-linked fatty acid. In myelin, hydroxylation of ceramide is exclusively found at the alpha-C atom of the fatty acid moiety. alpha-Hydroxylated cerebrosides are the most abundant lipids in the myelin sheath. The functional role of this modification, however, is not known. On the basis of sequence similarity to a yeast C26 fatty acid hydroxylase, we have identified a murine cDNA encoding FA2H (fatty acid 2-hydroxylase). Transfection of FA2H cDNA in CHO cells (Chinese-hamster ovary cells) led to the formation of alpha-hydroxylated fatty acid containing hexosylceramide. An EGFP (enhanced green fluorescent protein)-FA2H fusion protein co-localized with calnexin, indicating that the enzyme resides in the endoplasmic reticulum. FA2H is expressed in brain, stomach, skin, kidney and testis, i.e. in tissues known to synthesize fatty acid alpha-hydroxylated sphingolipids. The time course of its expression in brain closely follows the expression of myelin-specific genes, reaching a maximum at 2-3 weeks of age. This is in agreement with the reported time course of fatty acid alpha-hydroxylase activity in the developing brain. In situ hybridization of brain sections showed expression of FA2H in the white matter. Our results thus strongly suggest that FA2H is the enzyme responsible for the formation of alpha-hydroxylated ceramide in oligodendrocytes of the mammalian brain. Its further characterization will provide insight into the functional role of alpha-hydroxylation modification in myelin, skin and other organs. << Less

  Biochem. J. 388:245-254(2005) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Synthesis of monohydroxylated inositolphosphorylceramide (IPC-C) in Saccharomyces cerevisiae requires Scs7p, a protein with both a cytochrome b5-like domain and a hydroxylase/desaturase domain.

  Dunn T.M., Haak D., Monaghan E., Beeler T.J.

  Saccharomyces cerevisiae mutants lacking Scs7p fail to accumulate the inositolphosphorylceramide (IPC) species. IPC-C, which is the predominant form found in wild-type cells. Instead scs7 mutants accumulate an IPC-B species believed to be unhydroxylated on the amide-linked C26-fatty acid. Eliminat ... >> More

  Saccharomyces cerevisiae mutants lacking Scs7p fail to accumulate the inositolphosphorylceramide (IPC) species. IPC-C, which is the predominant form found in wild-type cells. Instead scs7 mutants accumulate an IPC-B species believed to be unhydroxylated on the amide-linked C26-fatty acid. Elimination of the SCS7 gene suppresses the Ca(2+)-sensitive phenotype of csg1 and csg2 mutants. The CSG1 and CSG2 genes are required for mannosylation of IPC-C and accumulation of IPC-C by the csg mutants renders them Ca(2+)-sensitive. The SCS7 gene encodes a protein that contains both a cytochrome b5-like domain and a domain that resembles the family of cytochrome b5-dependent enzymes that use iron and oxygen to catalyse desaturation or hydroxylation of fatty acids and sterols. Scs7p is therefore likely to be the enzyme that hydroxylates the C26-fatty acid of IPC-C. << Less

  Yeast 14:311-321(1998) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Fah1p, a Saccharomyces cerevisiae cytochrome b5 fusion protein, and its Arabidopsis thaliana homolog that lacks the cytochrome b5 domain both function in the alpha-hydroxylation of sphingolipid-associated very long chain fatty acids.

  Mitchell A.G., Martin C.E.

  A search of the Saccharomyces cerevisiae genome data base for cytochrome b5-like sequences identified a 1.152-kilobase pair open reading frame, located on chromosome XIII at locus YMR272C (FAH1). That gene encodes a putative 384-amino acid protein with an amino-terminal cytochrome b5 domain. The b ... >> More

  A search of the Saccharomyces cerevisiae genome data base for cytochrome b5-like sequences identified a 1.152-kilobase pair open reading frame, located on chromosome XIII at locus YMR272C (FAH1). That gene encodes a putative 384-amino acid protein with an amino-terminal cytochrome b5 domain. The b5 core domain shows a 52% identity and 70% similarity to that of the yeast microsomal cytochrome b5 and a 35% identity and 54% similarity to the b5 core domain of OLE1, the S. cerevisiae Delta-9 fatty acid desaturase. Expression of the S. cerevisiae FAH1 cytochrome b5 domain in Escherichia coli produces a soluble protein that exhibits the typical oxidized versus reduced differential absorbance spectra of cytochrome b5. Sequence analysis of Fah1p reveals other similarities to Ole1p. Both proteins are predicted to have two hydrophobic domains, each capable of spanning the membrane twice, and both have the HX(2-3)(XH)H motifs that are characteristic of membrane-bound fatty acid desaturases. These similarities to Ole1p suggested that Fah1p played a role in the biosynthesis or modification of fatty acids. Disruption of the FAH1 gene in S. cerevisiae did not give any visible phenotype, and there was no observable difference in content or distribution of the most abundant long chain saturated and unsaturated 14-18-carbon fatty acid species. Northern blot analysis, however, showed that this gene is expressed at much lower levels ( approximately 150-fold) than the OLE1 gene, suggesting that it might act on a smaller subset of fatty acids. Analysis of sphingolipid-derived very long chain fatty acids revealed an approximately 40-fold reduction of alpha-HO 26:0 and a complementary increase in 26:0 in the gene-disrupted fah1Delta strain. GAL1 expression of the S. cerevisiae FAH1 genes in the fah1Delta strain restores alpha-HO 26:0 fatty acids to wild type levels. Also identified are a number of homologs to this gene in other species. Expression of an Arabidopsis thaliana FAH1 gene, which does not contain the cytochrome b5 domain, in the fah1Delta strain produced an approximately 25-fold increase in alpha-HO 26:0 and reduced the levels of its 26-carbon precursor, suggesting that it functions in very long chain fatty acid hydroxylation using an alternate electron transfer mechanism. << Less

  J. Biol. Chem. 272:28281-28288(1997) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Stereospecificity of fatty acid 2-hydroxylase and differential functions of 2-hydroxy fatty acid enantiomers.

  Guo L., Zhang X., Zhou D., Okunade A.L., Su X.

  FA 2-hydroxylase (FA2H) is an NAD(P)H-dependent enzyme that initiates FA α oxidation and is also responsible for the biosynthesis of 2-hydroxy FA (2-OH FA)-containing sphingolipids in mammalian cells. The 2-OH FA is chiral due to the asymmetric carbon bearing the hydroxyl group. Our current study ... >> More

  FA 2-hydroxylase (FA2H) is an NAD(P)H-dependent enzyme that initiates FA α oxidation and is also responsible for the biosynthesis of 2-hydroxy FA (2-OH FA)-containing sphingolipids in mammalian cells. The 2-OH FA is chiral due to the asymmetric carbon bearing the hydroxyl group. Our current study performed stereochemistry investigation and showed that FA2H is stereospecific for the production of (R)-enantiomers. FA2H knockdown in adipocytes increases diffusional mobility of raft-associated lipids, leading to reduced GLUT4 protein level, glucose uptake, and lipogenesis. The effects caused by FA2H knockdown were reversed by treatment with exogenous (R)-2-hydroxy palmitic acid, but not with the (S)-enantiomer. Further analysis of sphingolipids demonstrated that the (R)-enantiomer is enriched in hexosylceramide whereas the (S)-enantiomer is preferentially incorporated into ceramide, suggesting that the observed differential effects are in part due to synthesis of sphingolipids containing different 2-OH FA enantiomers. These results may help clarify the mechanisms underlying the recently identified diseases associated with FA2H mutations in humans and may lead to potential pharmaceutical and dietary treatments. This study also provides critical information to help study functions of 2-OH FA enantiomers in FA α oxidation and possibly other sphingolipid-independent pathways. << Less

  J. Lipid Res. 53:1327-1335(2012) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.