title: Functions of the Clostridium acetobutylicium FabF and FabZ proteins in unsaturated fatty acid biosynthesis.
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.
  
  
  CONCLUSIONS
  Thus, C. acetobutylicium introduces the double of unsaturated fatty acids by use of a novel and unknown enzyme.
authors.affiliation: College of Life Science, South China Agricultural University, Guangzhou 510642, PR China. vermilionrock@yahoo.com
authors.forename: Lei
authors.initials: L
authors.lastname: Zhu
authors.forename: Juanli
authors.initials: J
authors.lastname: Cheng
authors.forename: Biao
authors.initials: B
authors.lastname: Luo
authors.forename: Saixiang
authors.initials: S
authors.lastname: Feng
authors.forename: Jinshui
authors.initials: J
authors.lastname: Lin
authors.forename: Shengbin
authors.initials: S
authors.lastname: Wang
authors.forename: John E
authors.initials: JE
authors.lastname: Cronan
authors.forename: Haihong
authors.initials: H
authors.lastname: Wang
mesh_terms: D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000201:enzymology* / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005810:Multigene Family
chemical_list: D001426:Bacterial Proteins; D005231:Fatty Acids, Unsaturated; D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase