| Molecular analysis of a bifunctional fatty acid conjugase/desaturase from tung. Implications for the evolution of plant fatty acid diversity. | |
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MedLine Citation:
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PMID: 12481086 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The seed oil derived from the tung (Aleurites fordii Hemsl.) tree contains approximately 80% alpha-eleostearic acid (18:3delta(9cis,11trans,13trans)), an unusual conjugated fatty acid that imparts industrially important drying qualities to tung oil. Here, we describe the cloning and functional analysis of two closely related Delta(12) oleate desaturase-like enzymes that constitute consecutive steps in the biosynthetic pathway of eleostearic acid. Polymerase chain reaction screening of a tung seed cDNA library using degenerate oligonucleotide primers resulted in identification of two desaturases, FAD2 and FADX, that shared 73% amino acid identity. Both enzymes were localized to the endoplasmic reticulum of tobacco (Nicotiana tabacum cv Bright-Yellow 2) cells, and reverse transcriptase-polymerase chain reaction revealed that FADX was expressed exclusively within developing tung seeds. Expression of the cDNAs encoding these enzymes in yeast (Saccharomyces cerevisiae) revealed that FAD2 converted oleic acid (18:1delta(9cis)) into linoleic acid (18:2delta(9cis,12cis)) and that FADX converted linoleic acid into alpha-eleostearic acid. Additional characterization revealed that FADX exhibited remarkable enzymatic plasticity, capable of generating a variety of alternative conjugated and delta(12)-desaturated fatty acid products in yeast cells cultured in the presence of exogenously supplied fatty acid substrates. Unlike other desaturases reported to date, the double bond introduced by FADX during fatty acid desaturation was in the trans, rather than cis, configuration. Phylogenetic analysis revealed that tung FADX is grouped with delta(12) fatty acid desaturases and hydroxylases rather than conjugases, which is consistent with its desaturase activity. Comparison of FADX and other lipid-modifying enzymes (desaturase, hydroxylase, epoxygenase, acetylenase, and conjugase) revealed several amino acid positions near the active site that may be important determinants of enzymatic activity. |
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Authors:
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John M Dyer; Dorselyn C Chapital; Jui-Chang W Kuan; Robert T Mullen; Charlotta Turner; Thomas A McKeon; Armand B Pepperman |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Plant physiology Volume: 130 ISSN: 0032-0889 ISO Abbreviation: Plant Physiol. Publication Date: 2002 Dec |
Date Detail:
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Created Date: 2002-12-13 Completed Date: 2003-05-30 Revised Date: 2010-09-14 |
Medline Journal Info:
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Nlm Unique ID: 0401224 Medline TA: Plant Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 2027-38 Citation Subset: IM |
Affiliation:
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United States Department of Agriculture-Agricultural Research Service Southern Regional Research Center, 1100 Robert E Lee Boulevard, New Orleans, Louisiana 70124, USA. jdyer@nola.srrc.usda.gov |
| Data Bank Information | |
Bank Name/Acc. No.:
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GENBANK/AF525534; AF525535 |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Aleurites
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enzymology*,
genetics Amino Acid Sequence Evolution, Molecular Fatty Acid Desaturases / genetics*, metabolism Fatty Acids / chemistry, metabolism* Gene Expression Regulation, Enzymologic Gene Expression Regulation, Plant Mass Spectrometry Molecular Sequence Data Phylogeny Plant Proteins / genetics, metabolism Saccharomyces cerevisiae / genetics, metabolism Seeds / growth & development Sequence Homology, Amino Acid Substrate Specificity |
| Chemical | |
Reg. No./Substance:
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0/Fatty Acids; 0/Plant Proteins; EC 1.14.19.-/Fatty Acid Desaturases |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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