Hydrogen Peroxide-mediated Oxidation of Indole-3-acetic Acid by Tomato Peroxidase and Molecular Oxygen

Kokkinakis, Demetri M.; Brooks, James L.

doi:10.1104/pp.64.2.220

Cited by 44 publications

(32 citation statements)

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“…Nevertheless, IAAoxidases were, at least partially, separated from peroxidases when they were purified from tobacco roots (28), from crown gall tissue culture cells (24), or from mung bean cotyledons (30). In this case (30), IAA oxidation was inhibited by H202 in contrast to the results cited above (9).…”

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confidence: 80%

“…The degradation of auxin by HRP may occur without added cofactors, and in the presence or absence of H202 (6). However, tomato peroxidases are dependent on the presence of H202 for the oxidation of IAA (9) and fail to catalyze the reaction in the presence of compounds such as 2,4-dichloro- 'Present address: Department of Botany. University of Georgia, Athens, GA 30602.…”

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confidence: 99%

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In Vitro Oxidation of Indoleacetic Acid by Soluble Auxin-Oxidases and Peroxidases from Maize Roots

Beffa¹,

Martin²,

Pilet³

1990

Plant Physiol.

101

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Soluble auxin-oxidases were extracted from Zea mays L. cv LGlI apical root segments and partially separated from peroxidases (EC 1.11.1.7) by size-exclusion chromatography. Auxinoxidases were resolved into one main peak corresponding to a molecular mass of 32.5 kilodaltons and a minor peak at 54.5 kilodaltons. Peroxidases were separated into at least four peaks, with molecular masses from 32.5 to 78 kilodaltons. In vitro activity of indoleacetic acid-oxidases was dependent on the presence of MnCI2 and p-coumaric acid. Compound(s) present in the crude extract and several synthetic auxin transport inhibitors (including 2,3,5-triiodobenzoic acid and N-1-naphthylphthalamic acid) inhibited auxin-oxidase activity, but had no effect on peroxidases. The products resulting from the in vitro enzymatic oxidation of [3H] indoleacetic acid were separated by HPLC and the major metabolite was found to cochromatograph with indol-3yl-methanol.Two pathways for the oxidative degradation of IAA have been established. The first involves oxidation of the indole nucleus (32) by a specific enzyme which catalyzes the formation of oxindole-3-acetic acid (OxIAA2; 23), whereas the second pathway consists of the oxidative decarboxylation of the side chain. Peroxidases (EC 1.11.1.7) from numerous plant species have been shown to catalyze this oxidative decarboxylation (27), leading to the formation of either indol3yl-methanol (17) or 3-methyleneoxindole (6). The ratio of the production of these last two compounds is influenced by several factors including the nature of the cofactors added to study the reaction in vitro, the pH, and the enzyme/substrate ratio (4, 26).The breakdown of IAA catalyzed by peroxidases has been studied in a number of systems, and the requirement for added cofactors and for H202 differs between species. The degradation of auxin by HRP may occur without added cofactors, and in the presence or absence of H202 (6). However, tomato peroxidases are dependent on the presence of H202 for the oxidation of IAA (9) and fail to catalyze the reaction in the presence of compounds such as 2,4-dichloro-'Present address:

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confidence: 80%

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confidence: 99%

In Vitro Oxidation of Indoleacetic Acid by Soluble Auxin-Oxidases and Peroxidases from Maize Roots

Beffa¹,

Martin²,

Pilet³

1990

Plant Physiol.

101

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“…The mechanism of oxidation of a plant hormone, IAA has been a subject of investigation by many plant physiologists (126)(127)(128)(129)(130)(131)(132)(133)(134)(135). It is now accepted that free radical species which are formed through catalysis of peroxidase are intermediates in the degradation of IAA (128)(129)(130)(131)(132)(133)(134).…”

Section: Metabolismmentioning

confidence: 99%

Physiological Aspects of Free-Radical Reactions

Yamazaki¹,

Tamura²,

Nakajima³

et al. 1985

Environmental Health Perspectives

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Enzymes which catalyze the formation of free radicals in vitro will catalyze similar reactions in vivo. We believe that the formation of some kinds of free radicals has definite physiological meanings in metabolism. In this sense, the enzymes forming such free radicals are concluded to be in evolutionally advanced states. Elaborated structure and function of enzymes such as horseradish peroxidase and microsomal flavoproteins support the idea. Deleterious and side reactions caused by free radicals are assumed to be minimized in vivo by localizing the reactions, but this assumption should be verified by future studies.

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“…Kokkinakis and Brooks (14) measured the oxidation of IAA in citrate buffer and found that the tomato enzyme was much less effective than horseradish peroxidase. They subsequently reported that the oxidation by tomato peroxidase was enhanced by the inclusion of peroxide in the reaction mixture (15). The reaction rate decreased sharply when peroxide in the mixture was exhausted.…”

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confidence: 99%

Anions Activate the Oxidation of Indoleacetic Acid by Peroxidases from Tomato and Other Sources

Pressey¹

1990

Plant Physiol.

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Anionic peroxidase from tomato (Lycopersicon esculentum) fruit oxidized indoleacetic acid (IAA) Peroxidase catalyzes a variety of reactions in vitro which may not have physiological functions in intact plants. One of these reactions is the oxidation of IAA in the presence of 02, Mn2+, and a monophenol (5,11,18,27 When tomatoes were extracted with water, two peroxidases were separated by gel filtration but only the larger enzyme oxidized IAA. Extraction of the same fruit with 0.2 M NaCl yielded the same peroxidases but both enzymes oxidized IAA. They observed that the effective peroxidases were optimally active at pH 6.1, or substantially higher than that for many other peroxidases (1 1, 24, 33). In the study of the effect of pH on the reaction, they used acetate buffer for the pH range of 4 to 6 and phosphate for higher pH. A possible explanation for the observed high pH optimum may be that the enzymes were more effective on IAA in phosphate than in acetate. Thomas and Jen (29) studied the oxidation of IAA by purified tomato peroxidase using phosphate buffer at pH 6. They confirmed that the enzyme was capable of oxidizing IAA in the presence of Mn2' and DCP,' and that peroxide was not required. During preliminary studies on the oxidation of IAA by tomato peroxidase, I observed that the rate of the reaction was dependent on the nature and concentration of the buffer. The reaction occurred very slowly in acetate at pH 3 to 6, but it proceeded rapidly when phosphate was included in the buffers. An examination of the reaction in other buffers led to the discovery that some anions have extraordinary effects on the oxidation of IAA by tomato peroxidase. The study was extended to oxidation of IAA by horseradish peroxidases and other porphyrin proteins. MATERIALS AND METHODS Purification of Tomato PeroxidaseOne kg of pericarp tissue from green tomato (Lycopersicon esculentum cv Sweet Chelsea) fruit was homogenized with 1 L of 0.2 M sodium acetate (pH 6.0), containing 1.0 M NaCl. The homogenate was stirred for 1 h at 3°C and centrifuged at 10,000g for 30 min. The supernatant solution was concentrated to 25 mL by ultrafiltration using a PM-10 membrane (Amicon Corp.) and dialyzed against 0.15 M NaCl. It was clarified by centrifugation and applied to a 5 x 40 cm column of Sephadex G-100 in 0. 15 M NaCl.

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Hydrogen Peroxide-mediated Oxidation of Indole-3-acetic Acid by Tomato Peroxidase and Molecular Oxygen

Cited by 44 publications

References 18 publications

In Vitro Oxidation of Indoleacetic Acid by Soluble Auxin-Oxidases and Peroxidases from Maize Roots

In Vitro Oxidation of Indoleacetic Acid by Soluble Auxin-Oxidases and Peroxidases from Maize Roots

Physiological Aspects of Free-Radical Reactions

Anions Activate the Oxidation of Indoleacetic Acid by Peroxidases from Tomato and Other Sources

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