InterPro domain: IPR006694

This entry includes fatty acid and carotene hydroxylases and sterol desaturases. Beta-carotene hydroxylase is involved in zeaxanthin synthesis by hydroxylating beta-carotene, but the enzyme may be involved in other pathways [ 1 ]. This family includes C-5 sterol desaturase [ 2 ] and C-4 sterol methyl oxidase (SMO) [ 3 , 4 ]. Members of this family are involved in cholesterol biosynthesis and biosynthesis a plant cuticular wax. These enzymes contain two copies of a HXHH motif. Members of this family are integral membrane proteins.

The plant SMO amino acid sequences possess three histidine-rich motifs (HX3H, HX2HH and HX2HH), characteristic of the small family of membrane-bound non-haem iron oxygenases that are involved in lipid oxidation [ 5 ].

1. Molecular characterization of the CER1 gene of arabidopsis involved in epicuticular wax biosynthesis and pollen fertility. Plant Cell 7, 2115-27
2. Delta7-sterol-C5-desaturase: molecular characterization and functional expression of wild-type and mutant alleles. Plant Mol. Biol. 39, 891-906
3. Plant sterol biosynthesis: identification of two distinct families of sterol 4alpha-methyl oxidases. Biochem. J. 378, 889-98
4. Enzymological properties of sterol-C4-methyl-oxidase of yeast sterol biosynthesis. Biochim. Biophys. Acta 1633, 106-17