The enzyme, characterized from plants, catalyses the hydroxylation of carbon 2 of long- or very-long-chain fatty acids attached to sphinganine during de novo ceramide synthesis. The enzyme requires an external cytochrome b5 as the electron donor. The newly introduced 2-hydroxyl group has R-configuration. cf. EC 220.127.116.11, 4-hydroxysphinganine ceramide fatty acyl 2-hydroxylase.