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Open Access Research article

Functions of the Clostridium acetobutylicium FabF and FabZ proteins in unsaturated fatty acid biosynthesis

Lei Zhu1, Juanli Cheng1, Biao Luo1, Saixiang Feng1, Jinshui Lin1, Shengbin Wang1, John E Cronan23 and Haihong Wang1*

Author Affiliations

1 College of Life Science, South China Agricultural University, Guangzhou 510642, PR China

2 Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

3 Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

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BMC Microbiology 2009, 9:119  doi:10.1186/1471-2180-9-119

Published: 4 June 2009

Abstract

Background

The original anaerobic unsaturated fatty acid biosynthesis pathway proposed by Goldfine and Bloch was based on in vivo labeling studies in Clostridium butyricum ATCC 6015 (now C. beijerinckii) but to date no dedicated unsaturated fatty acid biosynthetic enzyme has been identified in Clostridia. C. acetobutylicium synthesizes the same species of unsaturated fatty acids as E. coli, but lacks all of the known unsaturated fatty acid synthetic genes identified in E. coli and other bacteria. A possible explanation was that two enzymes of saturated fatty acid synthesis of C. acetobutylicium, FabZ and FabF might also function in the unsaturated arm of the pathway (a FabZ homologue is known to be an unsaturated fatty acid synthetic enzyme in enterococci).

Results

We report that the FabF homologue located within the fatty acid biosynthetic gene cluster of C. acetobutylicium functions in synthesis of both unsaturated fatty acids and saturated fatty acids. Expression of this protein in E. coli functionally replaced both the FabB and FabF proteins of the host in vivo and replaced E. coli FabB in a defined in vitro fatty acid synthesis system. In contrast the single C. acetobutylicium FabZ homologue, although able to functionally replace E. coli FabZ in vivo and in vitro, was unable to replace FabA, the key dehydratase-isomerase of E. coli unsaturated fatty acid biosynthesis in vivo and lacked isomerase activity in vitro.

Conclusion

Thus, C. acetobutylicium introduces the double of unsaturated fatty acids by use of a novel and unknown enzyme.