title: PUFA biosynthesis pathway in marine scallop Chlamys nobilis Reeve.
abstract: Long-chain polyunsaturated fatty acids (LC-PUFAs) are essential in important physiological processes. However, the endogenous PUFA biosynthesis pathway is poorly understood in marine bivalves. Previously, a fatty acyl desaturase (Fad) with Δ5 activity was functionally characterized and an elongase termed Elovl2/5 was reported to efficiently elongate 18:2n-6 and 18:3n-3 to 20:2n-6 and 20:3n-3 respectively in Chlamys nobilis. In this study, another elongase and another Fad were identified. Functional characterization in recombinant yeast showed that the newly cloned elongase can elongate 20:4n-6 and 20:5n-3 to C22 and C24, while the newly cloned scallop Fad exhibited a Δ8-desaturation activity, and could desaturate exogenously added PUFA 20:3n-3 and 20:2n-6 to 20:4n-3 and 20:3n-6 respectively, providing the first compelling evidence that noble scallop could de novo biosynthesize 20:5n-3 and 20:4n-6 from PUFA precursors though the "Δ8 pathway". No Δ6 or Δ4 activity was detected for this Fad. Searching against our scallop transcriptome database failed to find any other Fad-like genes, indicating that noble scallop might have limited ability to biosynthesize 22:6n-3. Interestingly, like previously characterized Elovl2/5, the two newly cloned genes showed less efficient activity toward n-3 PUFA substrates than their homologous n-6 substrates, resulting in a relatively low efficiency to biosynthesize n-3 PUFA, implying an adaption to marine environment.
authors.affiliation: Key Laboratory of Marine Biotechnology of Guangdong Province, Shantou University , Shantou, 515063, China.
authors.forename: Helu
authors.initials: H
authors.lastname: Liu
authors.forename: Hongkuan
authors.initials: H
authors.lastname: Zhang
authors.forename: Huaiping
authors.initials: H
authors.lastname: Zheng
authors.forename: Shuqi
authors.initials: S
authors.lastname: Wang
authors.forename: Zhicheng
authors.initials: Z
authors.lastname: Guo
authors.forename: Guofan
authors.initials: G
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D053898:Biosynthetic Pathways; D003001:Cloning, Molecular; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism; D015525:Fatty Acids, Omega-3 / Q000096:biosynthesis* / Q000737:chemistry; D008969:Molecular Sequence Data; D015394:Molecular Structure; D049897:Pectinidae / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D016415:Sequence Alignment
chemical_list: D015525:Fatty Acids, Omega-3; D044943:Fatty Acid Desaturases
keywords: Chlamys nobilis; PUFA biosynthesis; marine bivalve; Δ8 pathway