Gctgtcaaca cccatggctg agagctc nthg nthr gagctctcagccatgggtgttgacagc hthl gctgtccaca cccatggctg agagctc hthg hthr gagctctcagccatgggtgtggacagc nahl gctgtcaacg cccatggctg agagctc nahg nahr gagctctcagccatgggcgttgacagc nshr gctgtcaact cccatggctg agagctc nshg nshl gagctctcagccatgggagttgacagc athl gctgtcgc

0006-291X/$ see front matter 2013 Elsevier Inc. A http://dx.doi.org/10.1016/j.bbrc.2013.01.062 Abbreviations: D8D, D-sphingolipid desaturase; D LA, linoleic acid; ALA, a-linolenic acid; GLA, c-linole enoic acid; Cytb5, cytochrome b5; GC–MS, gas chrom try; aa, amino acid residue(s). q The work was carried out in Institute of Genetics Chinese Academy of Sciences, Beijing 100101, China. ⇑ Corresponding author. Address: Institute of G Biology, Chinese Academy of Sciences, Datun Road 100101, China. Fax: +86 10 64807626. E-mail addresses: lysong@genetics.ac.cn (L.-Y. S (W.-X. Lu), junhu7626@yahoo.com (J. Hu), wbyin yhchen@genetics.ac.cn (Y.-H. Chen), wangbailin1@12 Wang@ARS.USDA.GOV (R.R.-C. Wang), zmhu@genetic 1 These authors equally contributed to the research. D-fatty acid desaturase is an important enzyme in the catalytic synthesis of polyunsaturated fatty acids. Using domain swapping and a site-directed mutagenesis strategy, we found that the region of the C-terminal 67 amino acid residues of D-fatty acid desaturase RnD6C from blackcurrant was essential for its catalytic activity and that seven different residues between RnD6C and RnD8A in that region were involved in the desaturase activity. Compared with RnD6C, the activity of the following mutations, V394A, K395I, F411L, S436P, VK3945AI and IS4356VP, was significantly decreased, whereas the activity of I417T was significantly increased. The amino acids N, T and Y in the last four residues also play a certain role in the desaturase activity. 2013 Elsevier Inc. All rights reserved.