Document Detail


A peroxygenase pathway involved in the biosynthesis of epoxy fatty acids in oat.
MedLine Citation:
PMID:  21784965     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
While oat (Avena sativa) has long been known to produce epoxy fatty acids in seeds, synthesized by a peroxygenase pathway, the gene encoding the peroxygenase remains to be determined. Here we report identification of a peroxygenase cDNA AsPXG1 from developing seeds of oat. AsPXG1 is a small protein with 249 amino acids in length and contains conserved heme-binding residues and a calcium-binding motif. When expressed in Pichia pastoris and Escherichia coli, AsPXG1 catalyzes the strictly hydroperoxide-dependent epoxidation of unsaturated fatty acids. It prefers hydroperoxy-trienoic acids over hydroperoxy-dienoic acids as oxygen donors to oxidize a wide range of unsaturated fatty acids with cis double bonds. Oleic acid is the most preferred substrate. The acyl carrier substrate specificity assay showed phospholipid and acyl-CoA were not effective substrate forms for AsPXG1 and it could only use free fatty acid or fatty acid methyl esters as substrates. A second gene, AsLOX2, cloned from oat codes for a 9-lipoxygenase catalyzing the synthesis of 9-hydroperoxy-dienoic and 9-hydroperoxy-trienoic acids, respectively, when linoleic (18:2-9c,12c) and linolenic (18:3-9c,12c,15c) acids were used as substrates. The peroxygenase pathway was reconstituted in vitro using a mixture of AsPXG1 and AsLOX2 extracts from E. coli. Incubation of methyl oleate and linoleic acid or linolenic acid with the enzyme mixture produced methyl 9,10-epoxy stearate. Incubation of linoleic acid alone with a mixture of AsPXG1 and AsLOX2 produced two major epoxy fatty acids, 9,10-epoxy-12-cis-octadecenoic acid and 12,13-epoxy-9-cis-octadecenoic acid, and a minor epoxy fatty acid, probably 12,13-epoxy-9-hydroxy-10-transoctadecenoic acid. AsPXG1 predominately catalyzes intermolecular peroxygenation.
Authors:
Dauenpen Meesapyodsuk; Xiao Qiu
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Publication Detail:
Type:  Journal Article     Date:  2011-07-22
Journal Detail:
Title:  Plant physiology     Volume:  157     ISSN:  1532-2548     ISO Abbreviation:  Plant Physiol.     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-09-05     Completed Date:  2012-01-30     Revised Date:  2013-06-28    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  454-63     Citation Subset:  IM    
Affiliation:
Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5A8.
Data Bank Information
Bank Name/Acc. No.:
GENBANK/JN390966;  JN390967
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MeSH Terms
Descriptor/Qualifier:
Avena sativa / metabolism*
Base Sequence
Cloning, Molecular
DNA Primers
DNA, Complementary
Escherichia coli / genetics
Fatty Acids / metabolism*
Gas Chromatography-Mass Spectrometry
Lipoxygenases / metabolism
Mixed Function Oxygenases / genetics,  metabolism*
Molecular Sequence Data
Pichia / genetics
Plasmids
Substrate Specificity
Chemical
Reg. No./Substance:
0/DNA Primers; 0/DNA, Complementary; 0/Fatty Acids; EC 1.-/Mixed Function Oxygenases; EC 1.13.11.-/Lipoxygenases; EC 1.14.-/peroxygenase
Comments/Corrections

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