期刊
JOURNAL OF LIPID RESEARCH
卷 56, 期 12, 页码 2309-2321出版社
ELSEVIER
DOI: 10.1194/jlr.M062158
关键词
polyunsaturated fatty acids; linoleic acid; alpha-linolenic acid; arachidonic acid; eicosapentaenoic acid; chimera
资金
- National Natural Science Foundation of China [21276108, 31271812, 31471128]
- Program for New Century Excellent Talents [NCET-13-0831]
- Program for Changjiang Scholars and Innovative Research Team in University [IRT1249]
- Fundamental Research Funds for the Central Universities [JUSRP51320B]
The omega 6 and omega 3 pathways are two major pathways in the biosynthesis of PUFAs. In both of these, delta 6 desaturase (FADS6) is a key bifunctional enzyme desaturating linoleic acid or alpha-linolenic acid. Microbial species have different propensity for accumulating omega 6- or omega 3-series PUFAs, which may be determined by the substrate preference of FADS6 enzyme. In the present study, we analyzed the molecular mechanism of FADS6 substrate specificity. FADS6 cDNAs were cloned from Mortierella alpina (ATCC 32222) and Micromonas pusilla (CCMP1545) that synthesized high levels of arachidonic acid and EPA, respectively. M. alpina FADS6 (MaFADS6-I) showed substrate preference for LA; whereas, M. pusilla FADS6 (MpFADS6) preferred ALA. To understand the structural basis of substrate specificity, MaFADS6-I and MpFADS6 sequences were divided into five sections and a domain swapping approach was used to examine the role of each section in substrate preference. Our results showed that sequences between the histidine boxes I and II played a pivotal role in substrate preference. Based on our domain swapping results, nine amino acid (aa) residues were targeted for further analysis by site-directed mutagenesis. G194L, E222S, M227K, and V399I/I400E substitutions interfered with substrate recognition, which suggests that the corresponding aa residues play an important role in this process.
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