Identification of an essential sequence for dihydroceramide C-4 hydroxylase activity of mouse DES2

Although the amino acid sequences of mouse DES1 (MDES1) and DES2 (MDES2) have 63% sequence identity, their enzymatic characteristics are quite different. MDES1 exhibits high dihydroceramide Δ4-desaturase activity and very low C-4 hydroxylase activity, while MDES2 is similarly active as both a dihydroceramide Δ4-desaturase and a C-4 hydroxylase. We constructed several chimeras of MDES1 and MDES2 and identified a region important for C-4 hydroxylase activity in MDES2. This region contains the sequence XAFGY (X=T or A or V; Y=T or N) and occurs on the C-terminal side of the first His-box of MDES2. We confirmed the conservation of this region in DES2 family members sequenced from humans, pigs, rats, chickens, zebrafish, and Xenopus.