Hydrolyzes the sphingolipid ceramide into sphingosine and free fatty acid. Regulates sphingolipid homeostasis. Promotes oxidative stress resistance. an N-acylsphing-4-enine + H2O = a fatty acid + sphing-4-enine Additional isoforms seem to exist. Mostly expressed in stems, leaves, roots and siliques, and, to a lower extent, in flowers. Increased accumulation of hydroxyceramides. Enhanced sensitivity to oxidative stress induced by methyl viologen. Increased sensitivity to C2-ceramide induced cell death. Belongs to the neutral ceramidase family.