IAA-oxidase Activity Research Articles

The inhibition of peroxidase and indole-3-acetic acid oxidase activity by British Anti-Lewisite

British Anti-Lewisite (BAL) binds to horseradish peroxidase in a manner which results in inhibition of both peroxidatic and oxidative functions of the enzyme. BAL competes with hydrogen peroxide for binding on peroxidase, and the inhibition of peroxidatic activity is irreversible. Solutions of purified horseradish peroxidase and individually resolved peroxidase isozymes show a gradual loss of peroxidatic activity with time when incubated with BAL. In these same treatments, however, the inhibition of indole-3-acetic acid (IAA) oxidase activity is immediate. With increasing amounts of enzyme in the incubation mixture, IAA oxidase activity is not completely inhibited and is observed following a lag period in the assay which shortens with longer incubation times. Peroxidase activity during this same time interval shows a lag period which increases with longer incubation times. Lowering the pH removed the lag period for oxidase activity, but did not change the pattern of peroxidase activity. These results suggest that the sites for the oxidation of indole-3-acetic acid and for peroxidatic activity may not be identical in horseradish peroxidase isozymes.

Optimum Conditions for Indoleacetic Acid Oxidase Extraction from Betula Leaves

AbstractThis report deals with total extraction and activation of soluble indoleacetic acid oxidase from Betula alleghaniensis leaves as affected by different buffers, varying pH, phenol binder, detergent, plus volume and time parameters. For all buffers and pH levels tested, only tris pH 8 gave a high activity. This result was not a pH effect, since a wide‐range, citrate‐phosphate buffer at pH 8 gave a very low activity. Addition of a neutral detergent, Triton X‐100, to all buffers gave considerable activity in every case. Most activity with Triton X‐100 occurred at pH 6 and least at pH 8 regardless of buffer composition. A phenol binder, polyvinylpyrollidone, increased activity also, but less than the detergent Triton X‐100. Both of these compounds in combination gave an additive effect and the highest measure of enzyme activity. Further increases in measurable indoleacetic acid oxidase activity were obtained by using the best combination of these factors to determine the optium tissue: buffer ratio and optimum soaking time. Increases in activity of 70 and 60%, respectively, were achieved.

Der enzymatische Abbau der Indol-3-Essigsäure bei Phycomyces blakesleeanus BGFF.

Protein extracts of Phycomyces blakesleeanus are tested for peroxidase activity by guajacol-benzidine after fractionation by polyacrylamide-discelectrophoresis. Only a minor part of the protein zones shows very low peroxidase activity. The indole-3-acetic acid oxidase activity is determined spectrophotometrically. Fungus cultures from different growth conditions (light, dark, zinc sufficiency, and zinc deficiency) were used after separation in mycelium and sporangiophores. Sporangiophores have a noticeably higher indole-3-acetic acid oxidase activity than mycelium. Cultures with stronger sporangiophore growth evidently have lower indoleacetic acid oxidase activity than those with weaker sporangiophore development. We detected only minor indoleacetic acid oxidase activity in shake cultures with suppressed sporangiophore development. The inhibition of indoleacetic acid oxidase activity by gallic acid could be proved by in vitro tests.

Changes in Paramagnetic Manganese (Mn(II)) and Related Enzyme Activities in Isolated Cucumber Cotyledons During Growth

Changes» in the activities of IAA oxidase, peroxidase, and ascorbic acid utilization (AAU) and in the level of paramagnetic manganese (Mn(II)) have been studied during GA3-induced growth of the isolated cucumber cotyledons in light or dark. In dark-grown cotyledons, where GA3 fails to evoke any growth response, an initial decline in the Mn(II) content during the first 8 h is followed by a rise which approaches the control value between 12 and 24 h. A marked, almost linear increase is observed in Mn(II) levels from 48 h onwards. The initial decline in Mn(II) is accompanied by an increase in IAA oxidase activity and decreased AAU. The large increases obtained at later times, viz. 48 and 72 h, appear to be related primarily to the release of manganese due to the degradation of protein bodies which proceeds under the action of GA and also to increased AAU. The IAA oxidase and peroxidase activities are close to control during this period. In light, however, IAA oxidase and peroxidase activities show marked increase during the first 4 h but no significant changes are observed in Mn(II) level or AAU. The peak of Mn(II) observed at 8 h corresponds with lower activities of IAA oxidase and peroxidase but an increase in AAU. The changes in Mn(II) closely correspond with the changes in AAU in light, peroxidase and IAA oxidase activities keeping close to the control. It appears that GA action is related to increased Mn(II) due to increased AAU which may be coupled to the peroxidase-IAA oxidase system. The study confirms the postulate given by us in an earlier paper.

Bud development and flowering of Chrysanthemum morifolium in relation to some enzyme activities and to the copper, iron and manganese status

Abstract Bud formation and flowering of Chrysanthemum morifolium grown at different levels of Cu, Fe and Mn in a peat/sand substrate have been studied in relation to the micronutrient status of the plants and to the phenolase, peroxidase and IAA oxidase activities in the leaves. When iron levels were inadequate, bud formation was inhibited by the omission of copper but there was no effect of omitting copper when iron was fully adequate. Very few buds opened fully, however, wherever copper was omitted. The copper content of the plants grown without added copper (2.4 ppm) was well below the published ‘critical’ level and was unaffected by the other treatments, Phenolase activity in the leaves was markedly reduced by copper deficiency irrespective of the level of iron applied. When the level of copper was adequate, however, phenolase activity increased with the level of iron. Similar but less marked effects were observed with peroxidase and IAA oxidase. The significance of the results in relation to the mech...

Comparative aspects of root and root nodule secondary metabolism in alfalfa

l-phenylalanine ammonia lyase (PAL), indoleacetic acid oxidase (IAA oxidase), O-methyltransferase, peroxidase, total phenolics and total indoles were compared in roots and root nodules of alfalfa. PAL, O-methyl-transferase, total phenolics and total indoles were higher in nodules than in roots. Isolated bacteroids were assayed for O-methyltransferase, PAL, peroxidase and total phenolics, but their levels were either low or not detectable. Nodule leghemoglobin was separated by disc gel electrophoresis and found to have IAA oxidase activity. Phenolics, IAA oxidase and leghemoglobin appear to be interrelated in regulating indole levels in the nodule.

Effect of Gallic Acid on Dark-growth, IAA Oxidase and Peroxidase Activities in Trigonella foenum graecum L

Summary Gallic acid, an intermediate between phenols and tannins, inhibits dark enhanced growth which is believed to be partly under the control of endogenous gibberellins. IAA oxidase/peroxidase activities are differentially affected by gallic acid suggesting that the two enzymes are functionally different. Differential effect on peroxidase activity in vitro and in vivo suggests that the effect of gallic acid may not be same in the two systems. Inhibition of dark growth by gallic acid may be due to its interference with some growth reactions independent of IAA.

Effect of lunularic acid analogues on liverwort growth and IAA oxidation

The growth inhibitory activity of lunularic acid and a number of analogues has been examined in liverwort gemmaling and cress root growth tests. Lunularic acid was no more active than a wide range of similar compounds and no clear correlation between structure and activity was observed. The effects of these compounds, and of liverwort extracts, on in vitro IAA-oxidase activity was also examined.

Paradoxical Effects of Actinomycin-D in Rooting Hypocotyl Cuttings of Phaseolus mungo

Summary Hypocotyl cuttings of Phaseolus mungo rooted in water and most profusely in IAA. 1 mg/1 Act-D + IAA significantly increased rooting. The fluctuations of peroxidase, IAA oxidase and amylase activities appear to be associated with the production of roots through the regulation of endogenous contents of nutrition and auxin.

High Resolution of Peroxidase-Indoleacetic Acid Oxidase Isoenzymes from Horseradish by Isoelectric Focusing

Several improved techniques for isoelectric focusing of isoenzymes in polyacrylamide gel slabs were developed. Using these techniques, three commercial sources of horseradish peroxidase were each examined with three commercial sources of carrier ampholytes to determine their respective isoenzyme profiles.A much higher degree of isoenzyme resolution was obtained than reported previously. A composite of all of the various tests gave a total of 42 peroxidase isoenzymes. Commercial sources of horseradish peroxidase showed many similarities in their isoenzyme patterns, but their differences were sufficient to recognize each source easily. Isoenzyme patterns for all three sources spanned the entire pH range with all three sources of wide range carrier ampholytes. Only a few isoenzymes stained darkly. Most isoenzymes stained moderately to lightly, but all were well resolved. Gels stained for indoleacetic acid oxidase activity showed the same pattern as gels stained for peroxidase activity. This was true for all three commerial sources of the enzyme. The isoenzyme patterns obtained in each run were entirely reproducible, and linear pH gradients were obtained in all cases. Limitations in the pH range of the wide range carrier ampholytes relative to the isoelectric points of the extreme anodic and cathodic isoenzymes led to the adoption of a modified definition of focusing time. In addition, the labeling of isoenzymes commonly used in electrophoresis was adapted for labeling isoenzymes resolved by isoelectric focusing.

Preliminary characterization of peroxidase isozymes isolated from two flax genotrophs

Four peroxidase (EC 1.11.1.7) isozymes were isolated from each of two flax genotrophs. All four isozymes were glycoproteins and all exhibited indoleacetic acid (IAA) oxidase activity. The percentage purity of two of the isozymes was very high; these isozymes differed in percentage carbohydrate and in peroxidase and IAA oxidase specific activities. Three of the isozymes displayed molecular weight values of about 43 000; for the fourth, molecular weight was considerably higher. Corresponding isozymes from the genotrophs and from two other flax genotypes displayed molecular weight differences which corresponded to electrophoretic relative mobility differences. Enzyme yield per unit fresh weight was higher for one genotroph than the other, and the balance between peroxidase activity and IAA oxidase activity between the genotrophs was different.

Early Effects of Boron Deficiency on Indoleacetic Acid Oxidase Levels of Squash Root Tips

The indoleacetic acid (IAA) oxidase activity of root tips of boron-sufficient, -deficient, recovering, and IAA-treated boron-sufficient squash plants (Cucurbita pepo L.) was determined. Apical and subapical root sections displayed an increase in IAA oxidase activity between 6 and 9 hours after boron was withheld, and after 24 hours the activity of the apical sections showed a 20-fold increase over +B controls. Root elongation of -B plants was inhibited before an increase in oxidase activity could be detected. Roots of plants subjected to 12 hours of -B treatment and then transferred to +B treatment for recovery regained normal elongation rates and oxidase activity within 18 to 20 hours. IAA treatment of +B plants increased IAA oxidase activity of apical and subapical root sections and also inhibited root elongation and caused symptoms similar to -B treatments.These results have demonstrated the earliest enzymic change for intact boron-deficient plants. The results are in agreement with the theory that boron deficiency symptoms may be the result of supraoptimal endogenous levels of IAA. These high levels of IAA may inhibit cell division and lead to an induction of the IAA oxidase enzyme.

PROPERTIES OF IAA OXIDASE FROM RIPENING TOMATO FRUIT

An indoleacetic acid (IAA) oxidizing enzyme was isolated from the pericarp of ripening tomato fruit by column chromatography fractionation. IAA oxidase from extracts of tomato pericarp exists in a high molecular weight form (>200,000) or in a low molecular weight form (∼40,000) or both depending upon extraction procedures. When IAA was oxidized by the high molecular weight form of IAA oxidase, a relatively long lag time was observed. The low molecular weight form of IAA oxidase activity showed no lag or a very short, 1- to 2-minute lag period. Enzyme activity was optimal at pH 6.1 and was stimulated by 2,4-dichlorophenol (DCP) and MnCl2. Neither 3-methyleneoxindole nor indolealdehyde were found as a major IAA oxidation products. Moderate increase in activity of IAA oxidase activity was observed during ripening of tomato fruit.

Iaa oxidase and polyphenol oxidase activities of peanut peroxidase isozymes

Four anionic isozymes (A 1, A 2, A 4 and A 5) from peanut cells in suspension medium possessed IAA oxidase and polyphenol oxidase activities. The specific activities of each of the enzymes differed among the 4 isozymes. The pH optima established in these assays for peroxidase was acidic, for IAA oxidase neutral and for polyphenol oxidase alkaline. All 4 isozymes had different K m and V max for the enzyme activities of peroxidase and polyphenol oxidase. The sigmoid kinetics from the IAA oxidase assays for the isozymes probably indicates an allosteric nature.

Characterization of Mercury Toxicity in Rice (Oryza sativa L.) Seedlings

Summary The effects of toxic concentrations of mercuric chloride (HgCl 2 ) on the activity of several enzymes in germinating rice (Oryza sativa L.) are reported. The activity of catalase, peroxidase, IAA oxidase, IAA synthase and ascorbic acid oxidase increased in response to mercury addition. This behaviour of stimulated enzyme activity synchronized with the similar increase in soluble protein formation.

Auxin Metabolism in Developing Cotton Hairs

Growth parameters and auxin metabolism of developing cotton (Gossypium hirsutum L., cv. Sankar 5) fibre were studied in plants grown in the field. Fibre length and dry weight were plotted against boll age and fitted to the best-fit curves by computer curvilinear regression analysis. Based on this analysis, fibre development was divided into four phases: (i) initiation, (ii) elongation, (iii) secondary thickening, and (iv) maturation. Changes in IAA oxidase and peroxidase activity showed that IAA catabolism was low during the elongation phase, while during the phase of secondary thickening it was very high (four-fold increase). It is suggested that the level of IAA may regulate the termination of primary wall extension and the initiation of cellulose deposition in cotton fibre.

The Effect of Copper on IAA-Oxidase Activity in Root Tissue of Barley (Hordeum vulgare. c. v. Zephyr)

Summary Levels of IAA-oxidase activity in root preparations of copper-treated Barley plants and seedlings were found to be closely related to root copper content. At root copper contents below 1000 ppm, IAA-oxidase activity was promoted, but marked inhibition of enzyme activity occurred at root copper levels in excess of this. The results are discussed in terms of possible mechanisms of copper toxicity.

Manipulation of IAA‐Oxidase Activity and Auxin‐Deficiency Symptoms in Intact Cotton Plants with Manganese Nutrition

AbstractCotton (Gossypium hirsutum L. cv. Deltapine 15) seedlings were grown in solution culture in which the Mn2+ level was varied. Following an initial period, a series of shifts in manganese nutrition were employed, each lasting 14 days. Appearance was observed and fresh weight, IAA oxidase (IAAO), peroxidase and IAAO inhibitor levels were determined. After the initial 3 weeks of treatment, growth was negatively correlated with IAAO (or peroxidase) activity. All shifts in manganese nutrition resulted in predicted changes in IAAO activity, growth and plant appearance during a second 2‐week period of the experiment. Continuously deficient plants exhibited highest leaf abscission and IAA oxidase activity, and lowest growth of all treatments. Plants shifted from deficient to control levels of Mn2+ exhibited a marked decline in IAAO activity, increase in growth and absence of leaf abscission. Plants shifted from borderline deficiency to deficient Mn2+ exhibited a major increase in IAAO activity, reduction in growth and extensive leaf abscission. Control and borderline toxicity plants maintained normal IAAO activity, growth, and appearance. During a final 2‐week period, symptom expression was intensified. In particular, the initial borderline deficiency plants shifted to deficient levels of Mn2+ abscised most of those leaves that expanded after the shift in treatment. In addition, shifts of some plants to toxic Mn2+ levels during the third phase of the experiment produced a complete cycle of manipulation. Plants initially deficient in Mn2+ with high IAAO and low growth recovered growth and declined in IAAO when shifted to control Mn2+ and then suffered severe inhibition of growth and toxicity symptoms when shifted to high Mn2+.In all cases changes in enzyme activity, growth, leaf abscission and similar symptoms were most strongly expressed in the youngest tissue or that with the greatest potential for growth during the interval of a particular treatment. Since total growth, IAAO, leaf abscission, internode length and similar symptoms were consistently manipulated in both directions (increase or decrease in intensity or degree) by raising or lowering Mn2+ levels in the plant culture medium, we conclude that there is a causal relationship between IAAO and these responses that involves destruction of auxin.

Der Einfluß phenolischer Aktivatoren und Inhibitoren der IES-Oxydase-Aktivität auf die Adventivbewurzelung bei Tradescantia albiflora

Summary Phenolic promotors and inhibitors of IAA-oxidase activity stimulate the induction of adventitious roots in Tradescantia . The former are physiologically more effective with the exception of homovanillic acid, which is the strongest inductor although it inhibits IAA-oxidase activity. The growth of the adventitious roots is, on the other hand generally inhibited by all phenolic compounds. Some of these applied phenolic acids are native substances of the cuttings. Correlative to root promotion and the effect on IAA-oxidase activity is the increase of oxygen uptake by the nodes of Tradescantia after phenolic treatment. The relationship of this effect and of root induction to the uncoupling of oxidative phosphorylation is discussed.

Comparison of the effect of some phenolic compounds on wheat coleoptile section growth with their effect on iaa-oxidase activity

P-coumaric acid (HCA), 2,4-dichlorophenol (DCP) and resorcionol acted as cofactors for IAA-oxidase isolated from young wheat plants. Ferulic acid (FA) and 3,4-dihydroxybenzoic acid (DHBA) induced a lag phase prior to IAA oxidation. HCA, FA (0.2-1 mg ml-1) and DCP (0.03-1 mg ml-1) strongly inhibited wheat coleoptile section growth. DHBA (0.01-1 mg ml-1) slightly stimulated it and resorcinol was without effect. HCA inhibited IAA-induced growth of coleoptile sections and FA stimulated it at low IAA levels and inhibited it at higher ones. DHBA, DCP and resorcinol did not affect IAA-induced growth of coleoptile sections.