Synthesis and scavenging role of furan fatty acids
2014
Lemke, Rachelle A. S. | Peterson, Amelia C. | Ziegelhoffer, Eva C. | Westphall, Michael S. | Tjellström, Henrik | Coon, Joshua J. | Donohue, Timothy J.
Fatty acids play important functional and protective roles in living systems. This paper reports on the synthesis of a previously unidentified 19 carbon furan-containing fatty acid, 10,13-epoxy-11-methyl-octadecadienoate (9-(3-methyl-5-pentylfuran-2-yl)nonanoic acid) (19Fu-FA), in phospholipids from Rhodobacter sphaeroides. We show that 19Fu-FA accumulation is increased in cells containing mutations that increase the transcriptional response of this bacterium to singlet oxygen (¹O ₂), a reactive oxygen species generated by energy transfer from one or more light-excited donors to molecular oxygen. We identify a previously undescribed class of S-adenosylmethionine-dependent methylases that convert a phospholipid 18 carbon cis unsaturated fatty acyl chain to a 19 carbon methylated trans unsaturated fatty acyl chain (19M-UFA). We also identify genes required for the O ₂-dependent conversion of this 19M-UFA to 19Fu-FA. Finally, we show that the presence of ¹O ₂ leads to turnover of 19Fu-Fa in vivo . We propose that furan-containing fatty acids like 19Fu-FA can act as a membrane-bound scavenger of ¹O ₂, which is naturally produced by integral membrane enzymes of the R. sphaeroides photosynthetic apparatus.
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