Time Course of Induction of Cytochrome P-450, NADPH-Cytochrome <i>c</i> Reductase, and Cinnamic Acid Hydroxylase by Phenobarbital, Ethanol, Herbicides, and Manganese in Higher Plant Microsomes

Reichhart, Danièle; Salaün, Jean‐Pierre; Benveniste, Irène; Durst, Francis

doi:10.1104/pp.66.4.600

Cited by 103 publications

(59 citation statements)

References 26 publications

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“…Three types of induction have been recorded: following xenobiotic feeding; following feeding of natural plant secondary products (Hendry & Jones, 1984) and on fungal infection (Fujita, Oha & Unitani, 1982). In storage tissue, wounding, followed by ageing, induces cytochrome P-450 (Rich & Lamb, 1977;Salaun et al, 1978) and is further enhanced by feeding xenobiotics (Reichhart et al, 1980). Among the xenobiotics, 25 nmol MnClg causes a 3-fold increase in cytochrome P-450 concentration in wounded and aged artichoke tubers (Reichhart et al 1980), while 10% ethanol or 10% dimethyl sulphoxide cause a 3-fold rise in cytochrome P-450 in intact mung beans (Hendry & Jones, 1984) with smaller rises on feeding such xenobiotics as phenobarbital (a well-known P-450 inducer in man) and the herbicide Monuron (Reichhart et al, 1979).…”

Section: The Alternative To Enzymic Detoxificationmentioning

confidence: 99%

Why Do Plants Have Cytochrome P‐450? Detoxification Versus Defence

Hendry

1986

New Phytologist

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SUMMARYEvidence is presented which suggests that cytochrome P-450, in plants, probably functions as in all other eukaryotic organisms, principally as a detoxification mechanism. In plants this function is largely suppressed during tissue maturation coinciding with cell vacuolation. The consequential accumulation and isolation of potential toxins within vacuoles provides higher plants with an anti-herbivore defence of evolutionary significance.

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Section: The Alternative To Enzymic Detoxificationmentioning

confidence: 99%

Why Do Plants Have Cytochrome P‐450? Detoxification Versus Defence

Hendry

1986

New Phytologist

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“…C4H was assayed, as described previously (Reichhart et al, 1980). ECOD and EROD activities were determined fluorimetrically (Werck-Reichhart et al, 1990).…”

Section: Enzyme Assaysmentioning

confidence: 99%

“…For aging experiments tubers were sliced (1.5 mm thick), washed, and incubated for 48 h in aerated (4 dm3 min-l), distilled water containing various chemicals, as described previously (Reichhart et al, 1980). Chemicals tested as C4H effectors were prototype P450 inducers known to trigger different signal transduction pathways in animals and bacteria (phenobarbital, aminopyrine, P-naphthoflavone, isosafrole, 3-methylcholanthrene, benzo[a]pyrene, clofibrate, and DEHP) (Bresnick, 1993), plant metabolites (flavone and 8-methoxypsoralen), metals (MnCl,, HgCl,, and CdCl,), and agrochemicals (biphenyl, lindane, and NA), a11 known to induce animal or plant P450s (Reichhart et al, 1979;Fujita, 1985;Letteron et al, 1986;Fonne-Pfister et al, 1988;Borlakoglu and John, 1989;Siess et al, 1989;McFadden et al, 1990;Batard et al, 1995).…”

Section: Plant Materialsmentioning

confidence: 99%

Regulation of the Cinnamate 4-Hydroxylase (CYP73A1) in Jerusalem Artichoke Tubers in Response to Wounding and Chemical Treatments

et al. 1997

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Recherche Scientifique, 28 ~ frans-Cinnamate 4-hydroxylase (C4H) is a plant-specific cytochrome (P450) that is encoded by the gene CYP73A and catalyzes the second step of the multibranched phenylpropanoid pathway. lncreases in C4H activity in response to physical and chemical stresses have been well documented, but the mechanism of these increases has never been studied i n detail. This paper reports on the regulatory mechanism controlling C4H activity in Jerusalem artichoke (Helianfhus tuberosus) tubers in response to wounding and chemical treatments. We compared induction of C4H and other P450-catalyzed activities. C4H was moderately induced by chemicals relative t o other P450s. lncreases in enzyme activity, C4H protein, and transcripts were quantified and compared in tuber tissue 48 h after wounding and chemical treatments. Our data suggest that induction of the enzyme activity results primarily from gene activation. lime-course experiments were performed after wounding and aminopyrine treatment. Compared with wounded tissues, aminopyrine triggered an additional and delayed peak of transcript accumulation. l h e timing of the induced changes in activity, protein, and transcripts confirms that C4H induction results primarily from an increase in CYP73Al mRNA, in both wounded and aminopyrine-treated tissues. However, posttranscriptional mechanisms might also contribute to the regulation of C4H activity.P450s are ubiquitous enzymes that catalyze the activation of molecular oxygen and the insertion of one of its atoms into physiological and artificial substrates (Porter and Coon, 1991). In plants P450s perform many oxygenation reactions in secondary metabolism, in sterols and fatty acid derivative synthesis, and in the detoxification of xenobiotics (Bolwell et al., 1994;Durst and OKeefe, 1995). More than 16 P450-catalyzed reactions have been reported in the pathway leading to the biosynthesis of phenylpropanoids (Werck-Reichhart, 1995). The influx of metabolites into the pathway is controlled by a sequence of three catalytic steps leading from Phe to activated 4-coumaroyl COA. The second reaction of the sequence is catalyzed by a P450 called C4H. Complete cDNA sequences were recently reported for the enzymes from Jerusalem artichoke (Helianthus tuberosus; Teutsch et al., 1993), mung bean (Vigna radiata; Mizutani et al., 1993), and alfalfa (Medicago sativa;

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“…trans-Cinnamate hydroxylation was assayed as previously described [18] : 32 potential substrate molecule4 were tested using yeast-expressed CYP73, including 12 plant P4SO substrates, 4 other potential natural substrates and 16 xenobiotics. Assays were performed as in the references given in Tables 1 and 2.…”

Section: Enzyme Assaysmentioning

confidence: 99%

Catalytic Properties of the Plant Cytochrome P450 CYP73 Expressed in Yeast

Pierrel

Batard

Kazmaier³

et al. 1994

European Journal of Biochemistry

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114

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have been investigated. Microsomes from transformed yeast catalysed trans-cinnamate hydroxylation with high efficiency. CYP73 was highly specific for its natural substrate, and did not catalyse oxygenation of p-coumarate, benzoate, ferulate, naringenin or furanocoumarins. No metabolism of terpenoids or fatty acids, known substrates of plant P450s, was observed. CYP73 however demethylated the natural coumarin herniarin into umbelliferone. In addition, it was shown to oxygenate five xenobiotics and mechanism-based inactivators, including the herbicide chlorotoluron. All substrates of CYP73 were small planar aromatic molecules. Comparison of the kinetic parameters of CYP73 for its various substrates showed that, as expected, cinnamate was by far the best substrate of this P450. The physiological and toxicological significance of these observations are discussed.Cytochromes P450 form a large superfamily of several hundreds to several thousands of hemoproteins, involved in oxygen activation and oxygen tranfer into lipophilic molecules. They all share some sequence identity related to their common catalytic properties, i.e. heme and oxygen binding, electron transfer and oxygen activation [l]. Differences in their primary sequences usually reflect variations in specificity for substrates oxygenated. These differences may concern more than 80% of the amino acid sequence. However, the modification of a single amino acid residue can be sufficient to completely alter the substrate specificity of the enzyme 121.Full-length amino acid sequences presently available for plant P450s share less than 30% identity. This almost certainly implies great differences in the structures of their substrate binding sites. However, no relation between the structure of the enzymes and their catalytic activities has yet been established. CYP73 is the first DNA sequence coding for a plant P450 with an identified physiological function to have been isolated 131. It catalyses the 4-hydroxylation of trunscinnamic acid into p-coumaric acid. This hydroxylation is ductase (4-hydroxylating) (EC 1.14.13.11).the second reaction in the phenylpropanoid pathway. Cinnamate 4-hydroxylase (CA4H) is thus an obligatory step for the biosynthesis of lignin, a major component of the earth's total biomass. It is involved in the formation of most of the phenylpropanoid derivatives, essential for plant development, pigmentation and defense against both ultraviolet light and pathogens. Recent data [4-61 suggest that CA4H plays a central role in the regulation of the phenylpropanoid pathway. We, therefore, decided to establish more precisely which molecules are transformed by the enzyme or interfere with its catalytic activity. The determination of a population of substrates was also intended to provide information for analysis of the structurelfunction relationship of this plant P450. We devised an optimized system for the expression of CYP73 in Saccharomyces cerevisae [7]. This system provided yeast microsomes for which the only detectable P450 was CYP73. It routine...

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Time Course of Induction of Cytochrome P-450, NADPH-Cytochrome c Reductase, and Cinnamic Acid Hydroxylase by Phenobarbital, Ethanol, Herbicides, and Manganese in Higher Plant Microsomes

Cited by 103 publications

References 26 publications

Why Do Plants Have Cytochrome P‐450? Detoxification Versus Defence

Why Do Plants Have Cytochrome P‐450? Detoxification Versus Defence

Regulation of the Cinnamate 4-Hydroxylase (CYP73A1) in Jerusalem Artichoke Tubers in Response to Wounding and Chemical Treatments

Catalytic Properties of the Plant Cytochrome P450 CYP73 Expressed in Yeast

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