A cytochrome P450 monooxygenase involved in epidermal ceramide biosynthesis. Hydroxylates the terminal carbon (omega-hydroxylation) of ultra-long-chain fatty acyls (C28-C36) prior to ceramide synthesis (PubMed:26056268). Contributes to the synthesis of three classes of omega-hydroxy-ultra-long chain fatty acylceramides having sphingosine, 6-hydroxysphingosine and phytosphingosine bases, all major lipid components that underlie the permeability barrier of the stratum corneum (PubMed:26056268). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH-ferrihemoprotein reductase) (PubMed:26056268). O2 + reduced [NADPH--hemoprotein reductase] + triacontanoate = H(+) + H2O + omega-hydroxy-triacontanoate + oxidized [NADPH--hemoprotein reductase] an omega-methyl-ultra-long-chain fatty acid + O2 + reduced [NADPH--hemoprotein reductase] = an omega-hydroxy-ultra-long-chain fatty acid + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] The disease is caused by variants affecting the gene represented in this entry. Belongs to the cytochrome P450 family. A second transmembrane domain at positions 95-115 is predicted by three programs ESKW, MEMSAT and Phobius. However experimental evidence supports the presence of a single signal-anchor transmembrane domain at the N-terminus.