Involved in ceramide synthesis. octadecanoyl-CoA + sphing-4-enine = CoA + H(+) + N-octadecanoylsphing-4-enine eicosanoyl-CoA + sphing-4-enine = CoA + H(+) + N-eicosanoyl-sphing-4-enine hexadecanoyl-CoA + sphing-4-enine = CoA + H(+) + N-hexadecanoylsphing-4-enine Expressed in testis (PubMed:33077892). Expressed in the retina with higher expression levels in the macular than in the peripheral region (PubMed:33077892). The disease may be caused by variants affecting distinct genetic loci, including the gene represented in this entry.