Accumulation of Oxygenated Fatty Acids in Oat Lipids During Storage

Doehlert, Douglas C.; Angelikousis, Steven; Vick, Brian

doi:10.1094/cchem-05-10-0074

Cited by 19 publications

(12 citation statements)

References 25 publications

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“…These fatty acids are mainly present in neutral lipids such as triacylglycerols and diacylglycerols (Leonova et al, 2008;Doehlert et al, 2010). Oat has also been extensively used as an enzyme source to study their biosynthesis, catalyzed by peroxygenase activity (Heimann and Schreier, 1970;Heimann and Dresen, 1973;Hamberg and Hamberg, 1996;Leonova et al, 2008).…”

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confidence: 99%

A Peroxygenase Pathway Involved in the Biosynthesis of Epoxy Fatty Acids in Oat

Meesapyodsuk

Qiu

2011

Plant Physiology

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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 hydroperoxydienoic 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.

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A Peroxygenase Pathway Involved in the Biosynthesis of Epoxy Fatty Acids in Oat

Meesapyodsuk

Qiu

2011

Plant Physiology

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“…Both Graveland (1970) and Levandi et al (2009) reported the detection of epoxy fatty acids, which were not detected in our study. In an earlier study from this group, these epoxy fatty acids were detected in oats (Doehlert et al, 2010). Yet, in a subsequent study where lipids were extracted from oat/water slurries (Doehlert et al, 2010), it appeared that epoxy fatty acids had been hydrolyzed into dihydroxy fatty acids.…”

Section: Discussionmentioning

confidence: 92%

“…In an earlier study from this group, these epoxy fatty acids were detected in oats (Doehlert et al, 2010). Yet, in a subsequent study where lipids were extracted from oat/water slurries (Doehlert et al, 2010), it appeared that epoxy fatty acids had been hydrolyzed into dihydroxy fatty acids. We suspect that the dihydroxy fatty acid detected in this study is the product of the hydrolysis of an epoxy fatty acid.…”

Section: Discussionmentioning

confidence: 92%

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Oxygenated fatty acids isolated from wheat bran slurries

Şimşek

Doehlert

2014

International Journal of Food Sciences and Nutrition

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Oxygenated fatty acids are classified as secondary metabolites in wheat, produced by oxidation of free fatty acids (FFAs). Oxygenated fatty acids have significant impact on the organoleptic and sensory properties of food products and participate in regulation of defense and developmental processes in plants. The objective of this study was to identify oxygenated fatty acids from wheat flour slurries. Wheat bran/water slurries were incubated for 4 h and freeze dried. Total lipids were extracted in chloroform/methanol/water; and methylated and silylated FFAs were analyzed with gas chromatography/mass spectroscopy. Seven oxygenated fatty acids were identified, (A) 12,13-dihydroxy-9-octadecenoic acid, (B) 9-hydroxy-10,12-octadecadienoic acid, (C) 13-hydroxy-9cis,11trans-octadecadienoic acid, (D) 9,10,13-trihydroxy-11trans-octadecenoic acid, (E) 9,12,13-trihydroxy-10trans,15cis-octadecadienoic acid, (F) 10-oxo-13-hydroxy-11trans-octadecenoic acid and (G) 12-oxo-13-hydroxy-octadecanoic acid, in wheat bran slurries. Our results are important for whole wheat food applications since oxygenated fatty acids can result in bitter flavors in the final product.

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“…(3). Conditions for gas chromatography-mass spectrometry (GC-MS) were also identical to those described inDoehlert et al (3).…”

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Inhibition of Fusarium graminearum Growth in Flour Gel Cultures by Hexane-Soluble Compounds from Oat (Avena sativa L.) Flour

Doehlert

Rayas‐Duarte

McMullen

2011

Journal of Food Protection

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Fusarium head blight, incited by the fungus Fusarium graminearum, primarily affects wheat (Triticum aestivum) and barley (Hordeum vulgarum), while oat (Avena sativa) appears to be more resistant. Although this has generally been attributed to the open panicle of oats, we hypothesized that a chemical component of oats might contribute to this resistance. To test this hypothesis, we created culture media made of wheat, barley, and oat flour gels (6 g of flour in 20 ml of water, gelled by autoclaving) and inoculated these with plugs of F. graminearum from actively growing cultures. Fusarium growth was measured from the diameter of the fungal plaque. Plaque diameter was significantly smaller on oat flour cultures than on wheat or barley cultures after 40 to 80 h of growth. Ergosterol concentration was also significantly lower in oat cultures than in wheat cultures after growth. A hexane extract from oats added to wheat flour also inhibited Fusarium growth, and Fusarium grew better on hexane-defatted oat flour. The growth of Fusarium on oat flour was significantly and negatively affected by the oil concentration in the oat, in a linear relationship. A hexane-soluble chemical in oat flour appears to inhibit Fusarium growth and might contribute to oat's resistance to Fusarium head blight. Oxygenated fatty acids, including hydroxy, dihydroxy, and epoxy fatty acids, were identified in the hexane extracts and are likely candidates for causing the inhibition.

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Accumulation of Oxygenated Fatty Acids in Oat Lipids During Storage

Cited by 19 publications

References 25 publications

A Peroxygenase Pathway Involved in the Biosynthesis of Epoxy Fatty Acids in Oat

A Peroxygenase Pathway Involved in the Biosynthesis of Epoxy Fatty Acids in Oat

Oxygenated fatty acids isolated from wheat bran slurries

Inhibition of Fusarium graminearum Growth in Flour Gel Cultures by Hexane-Soluble Compounds from Oat (Avena sativa L.) Flour

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