Reaction: an ultra-long-chain fatty acyl-CoA + a sphingoid base = an ultra-long-chain ceramide + CoA
Glossary: a sphingoid base = an amino alcohol, composed predominantly of 18 carbon atoms, characterized by the presence of a hydroxyl group at C-1 (and often also at C-3), and an amine group at C-2.
an ultra-long-chain fatty acyl-CoA = an acyl-CoA with a chain length of 28 or longer.
Other name(s): mammalian ceramide synthase 3; sphingoid base N-ultra-long-chain fatty acyl-coA transferase; CERS3 (gene name)
Systematic name: ultra-long-chain fatty acyl-coA:sphingoid base N-acyltransferase
Comments: Mammals have six ceramide synthases that exhibit relatively strict specificity regarding the chain-length of their acyl-CoA substrates. Ceramide synthase 3 (CERS3) is the only enzyme that is active with ultra-long-chain acyl-CoA donors (C28 or longer). It is active in the epidermis, where its products are incorporated into acylceramides. CERS3 also accepts (2R)-2-hydroxy fatty acids and ω-hydroxy fatty acids, and can accept very-long-chain acyl-CoA substrates (see EC 184.108.40.2067, very-long-chain ceramide synthase). It can use multiple sphingoid bases including sphinganine, sphingosine, phytosphingosine, and (6R)-6-hydroxysphingosine.
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