Detailed Model of the Peroxidase-Catalyzed Oxidation of Indole-3-Acetic Acid at Neutral pH

and, Sergey N. Krylov; Dunford, H. Brian

doi:10.1021/jp9522270

Cited by 28 publications

(44 citation statements)

References 21 publications

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“…Wall peroxidases can catalyze the oxidative degradation of auxin (Krylov and Dunford, 1996;Gazarian et al, 1998;Potters et al, 2009), and by promoting increased lignification of cell walls in the Casparian strip, they could alter auxin transport, which passes through this region as it cycles between shootward and rootward transport in primary roots (Naseer et al, 2012). It seems likely, however, that these wall changes are kinetically downstream of the NO and ROS changes that take place in less than 30 min when they are induced by increased [eATP] (Salmi et al, 2013).…”

Section: Superoxide (Omentioning

confidence: 99%

Apyrase Suppression Raises Extracellular ATP Levels and Induces Gene Expression and Cell Wall Changes Characteristic of Stress Responses

Lim¹,

Wu²,

Yao³

et al. 2014

Plant Physiology

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Plant cells release ATP into their extracellular matrix as they grow, and extracellular ATP (eATP) can modulate the rate of cell growth in diverse tissues. Two closely related apyrases (APYs) in Arabidopsis (Arabidopsis thaliana), APY1 and APY2, function, in part, to control the concentration of eATP. The expression of APY1/APY2 can be inhibited by RNA interference, and this suppression leads to an increase in the concentration of eATP in the extracellular medium and severely reduces growth. To clarify how the suppression of APY1 and APY2 is linked to growth inhibition, the gene expression changes that occur in seedlings when apyrase expression is suppressed were assayed by microarray and quantitative real-time-PCR analyses. The most significant gene expression changes induced by APY suppression were in genes involved in biotic stress responses, which include those genes regulating wall composition and extensibility. These expression changes predicted specific chemical changes in the walls of mutant seedlings, and two of these changes, wall lignification and decreased methyl ester bonds, were verified by direct analyses. Taken together, the results are consistent with the hypothesis that APY1, APY2, and eATP play important roles in the signaling steps that link biotic stresses to plant defense responses and growth changes.

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Section: Superoxide (Omentioning

confidence: 99%

Apyrase Suppression Raises Extracellular ATP Levels and Induces Gene Expression and Cell Wall Changes Characteristic of Stress Responses

Lim¹,

Wu²,

Yao³

et al. 2014

Plant Physiology

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“…[5][6][7][8] In our previous papers we developed a model for the HRP-catalyzed IAA oxidation. [6][7][8] This model did not define the structures of the free radicals involved in the chain reaction. …”

Section: Mechanism Of Hrp-catalyzed Iaa Oxidationmentioning

confidence: 99%

“…A nonclassical part of the peroxidase pathway is a free radical chain reaction in which ROOH is regenerated. 2, [5][6][7][8] The oxidase pathway involves the ferrous enzyme and HRP-III. 3 The substrate of Fe 2+ -HRP is oxygen, and the substrate of HRP-III is IAA.…”

Section: Introductionmentioning

confidence: 99%

Accelerating Effect of Umbelliferone on Peroxidase-Catalyzed Oxidation of Indole-3-acetic Acid at Neutral pH

and

Dunford

1996

J. Phys. Chem.

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The acceleration by the phenol umbelliferone (7-hydroxycoumarin) of the horseradish peroxidase (HRP) catalyzed oxidation of indole-3-acetic acid (IAA) was studied at pH 7.4 using spectral and kinetic approaches. For the system 0.1 mM IAA/1 µM HRP/variable umbelliferone concentration, an increase in rate by a factor of 8 was reached in the presence of 1 µM umbelliferone; further increase of the umbelliferone concentration had no further effect. The rate constants for the peroxidase compounds I and II (HRP-I and HRP-II) reductions by umbelliferone in the absence of IAA were measured in the transient state as functions of the umbelliferone concentration. The plot of the pseudo-first-order rate constant k obs vs [umbelliferone] for HRP-I reduction was curved upward. This result implies that umbelliferone catalyzes its own oxidation by HRP-I. The bimolecular rate constant of the reduction of 1 µM HRP-I by 1 µM umbelliferone was estimated to be 1.1 × 10 5 M -1 s -1 . The plot of k obs vs [umbelliferone] was linear for HRP-II reduction, yielding a bimolecular rate constant of 1.7 × 10 5 M -1 s -1 . The influence of umbelliferone on the rates of HRP-I and HRP-II reduction by IAA was also studied. It was found that 1 µM umbelliferone accelerates the reduction of 1 µM HRP-I by a factor of 10 but did not influence the reduction of HRP-II by IAA. The influence of umbelliferone on the HRP-I reduction by umbelliferone and/or IAA suggests that HRP-I can bind umbelliferone at a site different from the active site, where it provides a beneficial conformational change. However, the binding of umbelliferone to native HRP was not observed. A detailed mechanism for the HRP-catalyzed oxidation of IAA, both in the absence and in the presence of umbelliferone, is presented. There are three umbelliferoneinduced accelerating effects: (i) the reduction of the rate-limiting HRP species, HRP-II, by umbelliferone, which increases the rate of enzyme turnover and hence the rate of IAA oxidation, (ii) the nonenzymatic oxidation of IAA by free radicals of umbelliferone formed in the HRP-catalyzed oxidation of umbelliferone, and (iii) umbelliferone-induced acceleration of the HRP-I reduction by IAA. The magnitudes of these three effects are similar.

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“…The following types of free radicals were documented to be formed during the reaction: radical cation of IAA (14-16), scat01 radical, peroxyl radicals (8,(13)(14)(15)(16) and superoxide anion radical ( 1 3). Organic hydroperoxide is formed during a free radical chain reaction accompanying enzymatic and probably photochemical IAA oxidation (7,12,17).…”

Section: Nature Of Xmentioning

confidence: 99%

OpticalIy Pumped Chemiluminescence of Indole‐3‐Acetic Acid

Krylov

Krylova

1996

Photochem & Photobiology

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Optically pumped chemiluminescence of indole‐3‐acetic acid (IAA) was observed and studied. Rose Bengal (RB) was used as a photosensitizer. Long‐lived chemiluminescence (CL) appeared after irradiation of the IAA/RB reaction mixture by monochromatic light at 550 nm (the maximum of RB absorption) or by visible light. The CL spectrum had a maximum at 480 nm. The kinetics of the CL decay were single exponential. Single‐exponential kinetics were characterized by two experimentally measured values: initial CL intensity and exponential lifetime of the CL decay. We studied the influence of five parameters: (1) the rate of irradiation fluence, (2) the time of irradiation, (3) RIB concentration, (4) IAA concentration and (5) buffer pH on the initial CL intensity and the CL lifetime. Initial CL intensity was proportional to the rate of irradiation fluence and the concentration of RB. Saturation was observed in dependencies of initial CL intensity on the time of irradiation, the concentration of IAA and the buffer pH. The lifetime of the CL decay decreased with increasing pH and did not depend on the other four parameters. The mechanism explaining the experimental results was suggested and detailed kinetic analysis was performed to prove the proposed mechanism. Quantum yield of the CL and five rate constants that are involved in the mechanism were determined.

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Detailed Model of the Peroxidase-Catalyzed Oxidation of Indole-3-Acetic Acid at Neutral pH

Cited by 28 publications

References 21 publications

Apyrase Suppression Raises Extracellular ATP Levels and Induces Gene Expression and Cell Wall Changes Characteristic of Stress Responses

Apyrase Suppression Raises Extracellular ATP Levels and Induces Gene Expression and Cell Wall Changes Characteristic of Stress Responses

Accelerating Effect of Umbelliferone on Peroxidase-Catalyzed Oxidation of Indole-3-acetic Acid at Neutral pH

OpticalIy Pumped Chemiluminescence of Indole‐3‐Acetic Acid

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