Structure and Function of Δ9-Fatty Acid Desaturase

Delta 9-Fatty acid desaturase (Delta 9-desaturase) is a rate-limiting enzyme of unsaturated fatty acid biosynthesis in animal cells and specifically introduces a cis-double bond at the Delta 9-position of acyl-CoA. Since the chemical structure of fatty acids determines the physicochemical properties of cellular membrane and modulates a broad range of cellular functions, double bond introduction into a fatty acid by Delta 9-desaturase should be specifically carried out. Reported crystal structures of stearoyl-CoA desaturase (SCD)1, one of the most studied Delta 9-desaturases, have revealed the mechanism underlying the determination of substrate preference, as well as the position (Delta 9) and conformation (cis) of double bond introduction. The crystal structures of SCD1 have also provided insights into the function of other Delta 9-desaturases, including Drosophila homologs. Moreover, the amino-terminal sequences of Delta 9-desaturases are shown to have unique roles in protein degradation. In this review, we introduce recent advances in the understanding of the function and regulation of Delta 9-desaturase from the standpoint of protein structure.