SCD1 (Stearoyl-CoAdesaturase 1; also AcylCoA desaturase, fatty acid desaturase, and Delta9 desaturase) is a 37-40kD member of the fatty acid desaturase family of enzymes. It is an ER-embedded protein that is expressed by multiple cell types, including adipocytes, hepatocytes, macrophages, endothelial and sebaceous gland cells. SCD1 catalyzes the formation of mono-unsaturated fatty acids from saturated fatty acids. It does so by generating a double bond between the C9 and C10 carbons of dietary and/or endogenously synthesized fatty acids. This creates either palmitoleic or oleic acid, 2 fatty acids that are optimally suited for either storage or inclusion into phospholipids. It also removes a potential source of inflammation, as saturated fatty acids are known to activate TLRs with the subsequent onset of inflammation. Human SCD1 is a 4-transmembrane (TM), 359aa protein. It contains a 71aa cytoplasmic N-terminus, followed by two TM segments (aa72-119) and an extended cytoplasmic region (aa120-216) that possesses three utilized Ser/Thr phosphorylation sites, two additional TM segments (aa217-273), and a C-terminal cytoplasmic tail (aa274-359) that contains most of the catalytic region. There is one potential isoform variant that shows 13aa substitution for aa295-359. Over aa141-221, human SCD1 shares 95% aa sequence identity with mouse SCD1.