Four Amino Acid Residues Influence the Substrate Chain-Length and Regioselectivity of Siganus canaliculatus Δ4 and Δ5/6 Desaturases

• Published in: Lipids Vol. 49; no. 4; pp. 357 - 367
• Main Authors: Lim, Ze Long, Senger, Toralf, Vrinten, Patricia
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.04.2014
• Subjects: Amino Acids - chemistry; Amino Acids - genetics; Amino Acids - metabolism; Animals; Biomedical and Life Sciences; Chain‐length; Desaturase; Fatty Acid Desaturases - chemistry; Fatty Acid Desaturases - genetics; Fatty Acid Desaturases - metabolism; Fatty Acids, Unsaturated - chemistry; Fatty Acids, Unsaturated - metabolism; Life Sciences; Lipidology; Medical Biochemistry; Medicinal Chemistry; Microbial Genetics and Genomics; Neurochemistry; Nutrition; Original Article; Perciformes; Regioselectivity; Siganus canaliculatus; Substrate Specificity; Regioselectivity; Desaturase; Substrate specificity; Chain-length
• ISSN: 0024-4201; 1558-9307
• DOI: 10.1007/s11745-014-3880-0

Although ω3- and ω6- desaturases have been well studied in terms of substrate preference and regiospecificity, relatively little is known about the membrane-bound, “front-end” long chain fatty acid desaturases, such as ∆4, Δ5 or Δ6 desaturases. The first vertebrate ∆4 desaturase was recently identified in the marine teleost fish Siganus canaliculatus ( S. canaliculatus ), which also possesses a bifunctional Δ5/6 desaturase. These two long chain polyunsaturated fatty acid desaturases are very different in terms of regiospecificity and substrate chain-length, but share an unusually high degree of amino acid identity (83 %). We took advantage of this similarity by constructing a series of chimeric enzymes, replacing regions of one enzyme with the corresponding sequence of the other. Heterologous expression of the chimeric series of enzymes in yeast indicated that the substitution of a four amino acid region was sufficient to convert a ∆4 desaturase to an enzyme with ∆6 desaturase activity, and convert a ∆5/6 desaturase to an enzyme with a low level of ∆4 desaturase activity. In addition, enzymes having both ∆4 and ∆6 desaturase activities were produced by single or double amino acid substitutions within this four-amino acid region.