Characterization of Stearoyl-CoA Desaturases from a Psychrophilic Antarctic Copepod, Tigriopus kingsejongensis

Abstract

Stearoyl-CoA desaturase is a key regulator in fatty acid metabolism that catalyzes the desaturation of stearic acid to oleic acid and controls the intracellular levels of monounsaturated fatty acids (MUFAs). Two types of stearoyl-CoA desaturases (SCD, Δ9 desaturases) were discovered from an Antarctic copepod, Tigriopus kingsejongensis, which were collected in a tidal pool near the King Sejong Station, King George Island, Antarctica. Full-length cDNA sequences of two TkSCDs (T. kingsejongensis SCDs) were obtained from next-generation sequencing and isolated by reverse transcription PCR. DNA sequence lengths of the open reading frames of TkSCD-1 and TkSCD-2 were determined to be 1,110 and 681 bp, respectively. The molecular weights deduced from the corresponding genes were estimated to be 43.1 kDa (TkSCD-1) and 26.1 kDa (TkSCD-2). The amino acid sequences were compared with those of fatty acid desaturases and sterol desaturases from various types of organisms and used to analyze the relationships among TkSCDs. The enzymatic functions of both stearoyl-CoA desaturases, as assessed by heterologous expression of recombinant proteins in Escherichia coli, revealed that the amount of C16:1 and C18:1 fatty acids increased by more than three-fold after induction with isopropyl β-D-thiogalactopyranoside. Especially, 19.36 ± 1.34% and 14.04 ± 1.41% of C18:1 fatty acids were produced in cells expressing TkSCD-1 and TkSCD-2, respectively. The results of this study suggest that both SCD genes from an Antarctic marine copepod encode a functional desaturase that is capable of increasing the amounts of palmitoleic fatty acids and oleic fatty acids in a prokaryotic expression system.