cd03508

The Delta4-sphingolipid Fatty Acid Desaturase (Delta4-sphingolipid-FADS)-like CD includes the integral-membrane enzymes, dihydroceramide Delta-4 desaturase, involved in the synthesis of sphingosine; and the human membrane fatty acid (lipid) desaturase (MLD), reported to modulate biosynthesis of the epidermal growth factor receptor; and other related proteins. These proteins are found in various eukaryotes including vertebrates, higher plants, and fungi. Studies show that MLD is localized to the endoplasmic reticulum. As with other members of this superfamily, this domain family has extensive hydrophobic regions that would be capable of spanning the membrane bilayer at least twice. Comparison of sequences also reveals the existence of three regions of conserved histidine cluster motifs that contain eight histidine residues: HXXXH, HXXHH, and HXXHH. These histidine residues are reported to be catalytically essential and proposed to be the ligands for the iron atoms contained within the homolog, stearoyl CoA desaturase.