α-Oxidation of Fatty Acids in Higher Plants

Hámberg, Mats; Sanz, Ana I.; Castresana, Carmen

doi:10.1074/jbc.274.35.24503

Cited by 138 publications

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References 48 publications

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“…In algae as well as in higher plants (5), it has been reported that a long-chain fatty aldehyde would be formed through decarboxylation of the corresponding 2-hydroperoxy fatty acid (Scheme 1). 2-Hydroperoxy fatty acids are chemically unstable and have a half-life time of ϳ30 min in an aqueous buffer at 23°C (11). Thus, to detect the unstable fatty acid 2-hydroperoxide, the fatty acid as a substrate was incubated with the purified enzyme on ice and the product was immediately esterified with ADAM.…”

Section: Resultsmentioning

confidence: 99%

“…The protein derived from the gene was expressed in insect cells and found to cause uptake of molecular oxygen in the presence of polyunsaturated fatty acids such as linoleic, linolenic, and arachidonic acids. Later, the protein was identified as fatty acid ␣-oxygenase, which catalyzes the conversion of linoleic acid and the other fatty acids into the corresponding (R)-2-hydroperoxy fatty acids (11). Interestingly, the primary structures of plant ␣-oxygenases show similarity with those of mammalian PGHSs, although the substrates and products of these two oxygenases are quite different from each other.…”

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confidence: 99%

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Catalytic Properties of Rice α-Oxygenase

Koeduka

Matsui

Akakabe

et al. 2002

Journal of Biological Chemistry

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Long-chain fatty acids can be metabolized to C n؊1 aldehydes by ␣-oxidation in plants. The reaction mechanism of the enzyme has not been elucidated. In this study, a complete nucleotide sequence of fatty acid ␣-oxygenase gene in rice plants (Oryza sativa) was isolated. The deduced amino acid sequence showed some similarity with those of mammalian prostaglandin H synthases (PGHSs). The gene was expressed in Escherichia coli and purified to apparently homogenous state. It showed the highest activity with linoleic acid and predominantly formed 2-hydroperoxide of the fatty acid (C n ), which is then spontaneously decarboxylated to form corresponding C n؊1 aldehyde. With linoleic or linoleic acids as a substrate, rice ␣-oxygenase formed no product having a max at approximately 234 nm, which indicated that the enzyme could not oxygenize the pentadiene system in the substrate. The spectroscopic feature of the purified enzyme in its ferrous state is similar to that of mammalian PGHS, whereas that of dithionite-reduced state showed significant difference. Site-directed mutagenesis revealed that His-158, Tyr-380, and Ser-558 were essential for the ␣-oxygenase activity. These residues are conserved in PGHS and known as a heme ligand, a source of a radical species to initiate oxygenation reaction and a residue involved in substrate binding, respectively. This finding suggested that the initial step of the oxygenation reaction in ␣-oxygenase has a high similarity with that of PGHS. The rice ␣-oxygenase activity was inhibited by imidazole but hardly inhibited by nonsteroidal anti-inflammatory drugs, such as aspirin, ibuprofen, and flurbiprofen, which are known as typical PGHS inhibitors. In addition, peroxidase activity could not be detected with ␣-oxygenase when palmitic acid 2-hydroperoxide was used as a substrate. From these findings, the catalytic resemblance between ␣-oxygenase and PGHS seems to be evident, although there still are differences in their substrate recognitions and peroxidation activities.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Catalytic Properties of Rice α-Oxygenase

Koeduka

Matsui

Akakabe

et al. 2002

Journal of Biological Chemistry

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“…Aliphatic shortand medium-chain aldehydes and alcohols are emitted by various plant parts and are probably formed by enzymatic reduction of the parent acyl CoAs (Flamini et al, 2007). Alternatively, alcohols can also be formed by ADH-mediated hydrogenation of aldehydes, and medium-chain aldehydes are intermediates of the a-oxidation cycle starting with common fatty acids (Hamberg et al, 1999). However, alcohols are less important as flavor molecules due to their high odor thresholds in comparison with their aldehyde homologues.…”

Section: Fatty Acid-derived and Other Lipophylic Flavor Compoundsmentioning

confidence: 99%

Biosynthesis of plant‐derived flavor compounds

Schwab¹,

Davidovich‐Rikanati²,

Lewinsohn³

2008

The Plant Journal

942

704

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SummaryPlants have the capacity to synthesize, accumulate and emit volatiles that may act as aroma and flavor molecules due to interactions with human receptors. These low-molecular-weight substances derived from the fatty acid, amino acid and carbohydrate pools constitute a heterogenous group of molecules with saturated and unsaturated, straight-chain, branched-chain and cyclic structures bearing various functional groups (e.g. alcohols, aldehydes, ketones, esters and ethers) and also nitrogen and sulfur. They are commercially important for the food, pharmaceutical, agricultural and chemical industries as flavorants, drugs, pesticides and industrial feedstocks. Due to the low abundance of the volatiles in their plant sources, many of the natural products had been replaced by their synthetic analogues by the end of the last century. However, the foreseeable shortage of the crude oil that is the source for many of the artifical flavors and fragrances has prompted recent interest in understanding the formation of these compounds and engineering their biosynthesis. Although many of the volatile constituents of flavors and aromas have been identified, many of the enzymes and genes involved in their biosynthesis are still not known. However, modification of flavor by genetic engineering is dependent on the knowledge and availability of genes that encode enzymes of key reactions that influence or divert the biosynthetic pathways of plant-derived volatiles. Major progress has resulted from the use of molecular and biochemical techniques, and a large number of genes encoding enzymes of volatile biosynthesis have recently been reported.

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“…PIOX belongs to a larger family of heme-containing proteins that oxygenate fatty acids (4), which include the mammalian cyclooxygenases (COX-1 and COX-2; (5)), linoleate diol synthase (LDS) from the fungus Gaeumannomyces graminis (6, 7), and a Pseudomonas alcalignes protein of unknown function encoded by OrfX (8). PIOX has also been identified in many plant species, including Nicotiana attenuata (9), Nicotiana tabacum (3), Arabidopsis thaliana (3, 10), O. sativa (11), Capsicum annuum (12), and Lycopersicon esculentum (13).PIOX utilizes stereoselective oxygenation to convert linoleic acid (LA) (18:2, n-6) and other fatty acid substrates to their corresponding 2R-hydroperoxides, generating a novel class of oxylipins (3,11,14,15). The resulting 2R-hydroperoxides undergo spontaneous decarboxylation to shorter aldehydes and fatty acids (11,14).…”

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confidence: 99%

His-311 and Arg-559 Are Key Residues Involved in Fatty Acid Oxygenation in Pathogen-inducible Oxygenase

Koszelak-Rosenblum

Krol

Simmons

et al. 2008

Journal of Biological Chemistry

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Pathogen-inducible oxygenase (PIOX) oxygenates fatty acids into 2R-hydroperoxides. PIOX belongs to the fatty acid ␣-dioxygenase family, which exhibits homology to cyclooxygenase enzymes (COX-1 and COX-2). Although these enzymes share common catalytic features, including the use of a tyrosine radical during catalysis, little is known about other residues involved in the dioxygenase reaction of PIOX. We generated a model of linoleic acid (LA) bound to PIOX based on computational sequence alignment and secondary structure predictions with COX-1 and experimental observations that governed the placement of carbon-2 of LA below the catalytic Tyr-379. Examination of the model identified His-311, Arg-558, and Arg-559 as potential molecular determinants of the dioxygenase reaction. Substitutions at His-311 and Arg-559 resulted in mutant constructs that retained virtually no oxygenase activity, whereas substitutions of Arg-558 caused only moderate decreases in activity. Arg-559 mutant constructs exhibited increases of greater than 140-fold in K m , whereas no substantial change in K m was observed for His-311 or Arg-558 mutant constructs. Thermal shift assays used to measure ligand binding affinity show that the binding of LA is significantly reduced in a Y379F/ R559A mutant construct compared with that observed for Y379F/R558A construct. Although Oryza sativa PIOX exhibited oxygenase activity against a variety of 14 -20-carbon fatty acids, the enzyme did not oxygenate substrates containing modifications at the carboxylate, carbon-1, or carbon-2. Taken together, these data suggest that Arg-559 is required for high affinity binding of substrates to PIOX, whereas His-311 is involved in optimally aligning carbon-2 below Tyr-379 for catalysis.Pathogen attack on plants brings about the activation of multiple enzyme systems that results in the production of oxylipins from 18 -22 carbon fatty acid precursors. The generation of these bioactive lipid mediators initiates and sustains the defense reaction of the plant against insects, bacteria, fungi, and other pathogens (1, 2). One of the enzymes up-regulated during the host defense response is pathogen-inducible oxygenase (PIOX), 2 which catalyzes a non-lipoxygenase type of fatty acid oxygenation (3). PIOX belongs to a larger family of heme-containing proteins that oxygenate fatty acids (4), which include the mammalian cyclooxygenases (COX-1 and COX-2; (5)), linoleate diol synthase (LDS) from the fungus Gaeumannomyces graminis (6, 7), and a Pseudomonas alcalignes protein of unknown function encoded by OrfX (8). PIOX has also been identified in many plant species, including Nicotiana attenuata (9), Nicotiana tabacum (3), Arabidopsis thaliana (3, 10), O. sativa (11), Capsicum annuum (12), and Lycopersicon esculentum (13).PIOX utilizes stereoselective oxygenation to convert linoleic acid (LA) (18:2, n-6) and other fatty acid substrates to their corresponding 2R-hydroperoxides, generating a novel class of oxylipins (3,11,14,15). The resulting 2R-hydroperoxides undergo spontaneous deca...

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α-Oxidation of Fatty Acids in Higher Plants

Cited by 138 publications

References 48 publications

Catalytic Properties of Rice α-Oxygenase

Catalytic Properties of Rice α-Oxygenase

Biosynthesis of plant‐derived flavor compounds

His-311 and Arg-559 Are Key Residues Involved in Fatty Acid Oxygenation in Pathogen-inducible Oxygenase

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