This superfamily 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. This family includes C-5 sterol desaturase and C-4 sterol methyl oxidase. 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.