Hydrolyzes the sphingolipid ceramide into sphingosine and free fatty acid. Uses ceramide instead of phytoceramide as substrate. an N-acylsphing-4-enine + H2O = a fatty acid + sphing-4-enine Enhanced activity in the presence of calcium, magnesium, manganese and zinc ions, but inhibited activity in the presence of iron ion. Optimum pH is 5.7-6. A number of isoforms are produced. According to EST sequences. Expressed in seedlings, with higher levels in roots than in shoots. Belongs to the neutral ceramidase family.