label: sphingolipid delta-4 desaturase activity
label_lc: sphingolipid delta-4 desaturase activity
description: "Catalysis of the reaction: a dihydroceramide + 2 ferrocytochrome b5 + O2 + 2 H+ -> a sphingosine ceramide (aka (4E)-sphing-4-enine ceramide) + 2 ferricytochrome b5 + 2 H2O."