Sphingolipids are important membrane signalling molecules involved in many different cellular functions in eukaryotes. Sphingolipid delta 4-desaturase catalyses the formation of (E)-sphing-4-enine [1]. Some proteins in this family have bifunctional delta 4-desaturase/C-4-hydroxylase activity. Delta 4-desaturated sphingolipids may play a role in early signalling required for entry into meiotic and spermatid differentiation pathways during Drosophila spermatogenesis [1]. This small domain associates with FA_desaturase Pfam:PF00487 and appears to be specific to sphingolipid delta 4-desaturase.

1: Identification and characterization of a sphingolipid delta 4-desaturase family. Ternes P, Franke S, Zahringer U, Sperling P, Heinz E; J Biol Chem 2002;277:25512-25518. PMID:11937514