Cloning, tissue distribution, functional characterization and nutritional regulation of Δ6 fatty acyl desaturase in chu's croaker Nibea coibor

In the present study, we successfully cloned the full-length cDNA of a Δ6 fatty acyl desaturase (Δ6 Fad) of chu's croaker Nibea coibor. The cloned cDNA sequence was 1590 bp at full length, including a 5′-UTR of 137 bp, a 3′-UTR of 115 bp and a mean ORF of 1338 bp that specified a peptide of 445 aa. Sequence analysis of the deduced polypeptide showed that it contained all the characteristics of ∆ 6 Fad identified such as one cytochrome b5 domain, three trans-membrane regions and three histidine-rich boxes. Tissue distribution revealed that it strongly expressed in brain, significantly high than the level in eye, spleen, intestine, heart, gill, liver, stomach, muscle, liver and kidney. Functional characterization by heterologous expression in yeast showed that the chu's croaker desaturase was a Fad2 with ∆ 6 Fad activity, with 9.36% conversion of 18:2n-6 to 18:3n-6 and 4.93% of 18:3n-3 to 18:4n-3, respectively. Nutritional study showed that the expression of ∆ 6 Fad in liver were not significantly affected among treatments.