DEGS2 (sphingolipid C4-hydroxylase 2 / “degenerative spermatocyte homolog 2”) enzyme associated with the cytosolic face of the endoplasmic reticulum catalyzes the hydroxylation of dihydroceramide to form phytoceramide (Mizutani et al. 2004). DEGS2 appears not to be essential, with another unknown enzyme catalyzing the same reaction. The highest activity of DEGS2 is on long-chain (>= C21) dihydroceramides. DEGS2 also catalyzes the C4-dehydrogenation of dihydroceramide, but this activity is minor (Ota et al., 2023).