Ceramide synthase that catalyzes formation of ceramide from sphinganine and acyl-CoA substrates, with high selectivity toward long and very-long chains (C18:0-C22:0) as acyl donor. octadecanoyl-CoA + sphinganine = CoA + H(+) + N-(octadecanoyl)-sphinganine eicosanoyl-CoA + sphinganine = CoA + H(+) + N-eicosanoylsphinganine docosanoyl-CoA + sphinganine = CoA + H(+) + N-docosanoylsphinganine sphinganine + tetracosanoyl-CoA = CoA + H(+) + N-tetracosanoylsphinganine hexacosanoyl-CoA + sphinganine = CoA + H(+) + N-hexacosanoylsphinganine a fatty acyl-CoA + sphing-4-enine = an N-acylsphing-4-enine + CoA + H(+) octadecanoyl-CoA + sphing-4-enine = CoA + H(+) + N-octadecanoylsphing-4-enine hexadecasphinganine + octadecanoyl-CoA = CoA + H(+) + N-octadecanoylhexadecasphinganine Lipid metabolism; sphingolipid metabolism. The last loop motif confers selectivity toward stearoyl-CoA (octadecanoyl-CoA; C18:0-CoA) to behenoyl-CoA (docosanoyl-CoA; C22:0-CoA) as acyl donors. Phosphorylated at the C-terminus by CK2. N-glycosylated. Some prediction bioinformatics tools predict the presence of a homeobox domain (By similarity). However, the domain is degenerate and residues that are important for DNA-binding are absent (By similarity).