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Molecular cloning and functional characterization of the fatty acid delta 6 desaturase ( FAD 6 ) gene in the sea cucumber Apostichopus japonicus
Author(s) -
Liu Xiaoyu,
Wang Lin,
Feng Zhengfu,
Song Xiaojun,
Zhu Wei
Publication year - 2017
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.13317
Subject(s) - apostichopus japonicus , biology , sea cucumber , biochemistry , pichia pastoris , linoleic acid , polyunsaturated fatty acid , fatty acid desaturase , arachidonic acid , eicosapentaenoic acid , fatty acid , docosahexaenoic acid , open reading frame , amino acid , complementary dna , peptide sequence , recombinant dna , gene , enzyme , ecology
The sea cucumber ( Apostichopus japonicus ), an important echinodermata, had high value in nutrition and medicine for its rich collagen, sulphated polysaccharide, glycosides and polyunsaturated fatty acids ( PUFA ). The cDNA of the fatty acid desaturase gene in A. japonicus ( AJFAD 6 ) was cloned and was found to encode a desaturase with delta 6 FAD activity. Sequence analysis indicated that AJFAD 6 included an open reading frame of 1392 bp, encoding 463 amino acids. AJFAD 6 has all the conserved motifs found in other members of the FAD 6 family, including an N‐terminal cytochrome b5 domain and three histidine‐rich regions. qRT ‐ PCR showed that AJFAD 6 was expressed in all tissues tested during juvenile development and was mainly expressed in the respiratory tree at 150 days after adherence (150 days) and in the intestine at 100 days. Furthermore, AJFAD 6 mRNA was also detected in the analysed adult tissues, with higher expression in the intestine and testis. Functional characterization of AJFAD 6 in a recombinant yeast, Pichia pastoris , showed that AJFAD 6 could catalyse exogenous linoleic acid ( LA ) and α‐linolenic acid ( ALA ) to produce γ‐linoleic acid ( GLA ) and stearidonic acid ( STA ), respectively, at conversion rates of 11.1% for LA to GLA and 3.4% for ALA to STA . Our results suggested that the biosynthetic pathway of PUFA existed in the sea cucumber, but endogenous production of eicosapentaenoic acid, arachidonic acid and docosahexaenoic acid from either LA or ALA precursor appeared to be limited.