title: The human FA2H gene encodes a fatty acid 2-hydroxylase.
abstract: 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: Nathan L
authors.initials: NL
authors.lastname: Alderson
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Rembiesa
authors.forename: Michael D
authors.initials: MD
authors.lastname: Walla
authors.forename: Alicja
authors.initials: A
authors.lastname: Bielawska
authors.forename: Jacek
authors.initials: J
authors.lastname: Bielawski
authors.forename: Hiroko
authors.initials: H
authors.lastname: Hama
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002384:Catalysis; D002462:Cell Membrane / Q000378:metabolism; D002518:Ceramides / Q000737:chemistry / Q000378:metabolism; D002853:Chromatography, Liquid; D015786:Cytochromes b5 / Q000737:chemistry; D019992:Databases as Topic; D005227:Fatty Acids / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D008861:Microsomes / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009186:Myelin Sheath / Q000737:chemistry; D009249:NADP / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution; D014162:Transfection
chemical_list: D002518:Ceramides; D005227:Fatty Acids; D009249:NADP; D015786:Cytochromes b5; D006899:Mixed Function Oxygenases; C019081:fatty acid alpha-hydroxylase