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. {ECO:0000269|PubMed:17977534, ECO:0000269|PubMed:23530041, ECO:0000269|PubMed:26887952, ECO:0000269|PubMed:29632068, ECO:0000269|PubMed:31916624}. This is the function of Ensembl gene identifier ENSG00000090661 (CERS4, ceramide synthase 4).