Unusually large numbers of electrons for the oxidation of polyphenolic antioxidants

Hotta, Hiroki; Sakamoto, Hirotoshi; Nagano, Satomi; Osakai, Toshiyuki; Tsujino, Yoshio

doi:10.1016/s0304-4165(01)00123-4

Cited by 151 publications

(110 citation statements)

References 55 publications

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“…The first is the respective roles of shikimate and quinate esters. If shikimate esters are described as transient intermediates, quinate derivatives such as chlorogenic acid commonly accumulate in some plant species and are alternatively described as growth regulators, disease resistance factors, antioxidants, and compounds affecting organoleptic quality of fruits (36,38,54,55 This leads to another interesting question concerning the branching of the pathway downstream of C3ЈH. Our data and previous reports (17,51) seem to indicate that the shikimate and quinate esters are not substrates of CCoAOMTs.…”

Section: Cyp98a3 a 3ј-hydroxylase Of P-coumaroyl Esters In Arabidopsissupporting

confidence: 52%

CYP98A3 from Arabidopsis thaliana Is a 3′-Hydroxylase of Phenolic Esters, a Missing Link in the Phenylpropanoid Pathway

Schoch

Goepfert

Morant

et al. 2001

Journal of Biological Chemistry

405

370

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The 4-and 5-hydroxylations of phenolic compounds in plants are catalyzed by cytochrome P450 enzymes. The 3-hydroxylation step leading to the formation of caffeic acid from p-coumaric acid remained elusive, however, alternatively described as a phenol oxidase, a dioxygenase, or a P450 enzyme, with no decisive evidence for the involvement of any in the reaction in planta. In this study, we show that the gene encoding CYP98A3, which was the best possible P450 candidate for a 3-hydroxylase in the Arabidopsis genome, is highly expressed in inflorescence stems and wounded tissues. Recombinant CYP98A3 expressed in yeast did not metabolize free pcoumaric acid or its glucose or CoA esters, p-coumaraldehyde, or p-coumaryl alcohol, but very actively converted the 5-O-shikimate and 5-O-D-quinate esters of trans-p-coumaric acid into the corresponding caffeic acid conjugates. The shikimate ester was converted four times faster than the quinate derivative. Antibodies directed against recombinant CYP98A3 specifically revealed differentiating vascular tissues in stem and root. Taken together, these data show that CYP98A3 catalyzes the synthesis of chlorogenic acid and very likely also the 3-hydroxylation of lignin monomers. This hydroxylation occurs on depsides, the function of which was so far not understood, revealing an additional and unexpected level of networking in lignin biosynthesis.Systematic genome sequencing is revealing a large number of orphan genes and their phylogenetic relatedness to genes with characterized function. EST 1 sequences, on the other hand, are providing preliminary information on levels, patterns of expression, and conservation of genes among species. Taken together, such information can be exploited as a clue to gene function and to track down missing steps in important pathways.The sequencing of the whole genome of Arabidopsis thaliana has revealed 273 cytochrome P450 genes distributed into 45 families and subfamilies (drnelson.utmem.edu/CytochromeP450. html, www.biobase.dk/P450/). P450 proteins thus form the largest superfamily of enzymes involved in plant metabolism, but the function of 80% of these enzymes is still unknown. Our attention was first drawn to the CYP98 family by its phylogeny and structure. An analysis of P450 phylogeny in A. thaliana (Fig. 1) shows that the CYP98 family is most closely related to CYP73A5, coding for the cinnamic-acid 4-hydroxylase, the second enzyme and first P450 in the phenylpropanoid pathway (1). CYP73A5 and the CYP98 family seem to have evolved from the same ancestor as CYP79 enzymes, some of which also, in common with CYP73A5, use aromatic substrates derived from the shikimate pathway (2, 3). It was thus tempting to speculate that the substrate of CYP98 enzymes was derived from aromatic amino acids as well. The Arabidopsis CYP98 family is formed by only three genes. CYP98A3 is present in single copy; CYP98A8 and CYP98A9 are 69% identical to one another and only 52% identical to CYP98A3. All P450 genes in the phenylpropanoid pathway (CYP73A5, CYP84A1, and CYP...

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Section: Cyp98a3 a 3ј-hydroxylase Of P-coumaroyl Esters In Arabidopsissupporting

confidence: 52%

CYP98A3 from Arabidopsis thaliana Is a 3′-Hydroxylase of Phenolic Esters, a Missing Link in the Phenylpropanoid Pathway

Schoch

Goepfert

Morant

et al. 2001

Journal of Biological Chemistry

405

370

View full text Add to dashboard Cite

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“…[14][15][16][17] Cyclic voltammograms were recorded with a 315A potentiostat (Huso Electrochemical System, Kawasaki, Japan), in methanol : 0.1 M phosphate buffer (pH 7.5), (1 : 1, v/v). A glassy carbon (GC) electrode served as the working electrode, an Ag/AgCl electrode was used as the reference electrode, and a platinum electrode was used as a counter electrode.…”

Section: Treatment Of Cells With Hepatotoxin In the Presence Of Egcg mentioning

confidence: 99%

Enhancing Effect of Zinc on Hepatoprotectivity of Epigallocatechin Gallate in Isolated Rat Hepatocytes.

Kagaya

Kawase

Maeda

et al. 2002

Biological & Pharmaceutical Bulletin

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“…While the eventually formed quinones are stable within the pulse-radiolytic time frame, evidence from the literature suggests that slow dimerization reactions occur via various mesomeric semiquinone structures (24,32,33). …”

Section: Discussionmentioning

confidence: 99%

“…Monophasic behavior occurs whenever one reaction dominates strongly over the others. Potential dimerization (24,32,33) instead of disproportionation -with the focal point being the 'CaffCβda' mesomeric structure (top right in Scheme II) -would not be apparent in the kinetic model as both are second-order processes. As shown in Table III, the DFT calculations support the distinction between the different stabilities of the mesomers, with a far superior electron delocalization (hence resonance stabilization of the radical) of the respective O 4 -semiquinones.…”

Section: Gmentioning

confidence: 99%

Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

et al. 2004

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Caffeic acid, rosmarinic acid and oligomers of caffeic acid with multiple catechol groups are all constituents of Salvia officinalis. Their antioxidant potential was investigated with regard to their radical scavenging activity and the stability and structure of the intermediate radicals. Pulse-radiolytic studies revealed very high rate constants with hydroxyl radicals. Evidence from kinetic modeling calculations suggested an unusual complex behavior due to the presence of both O 4 -and O 3 -semiquinones and formation and decay of a hydroxyl radical adduct at the vinyl side chain. The radical structures observed by EPR spectroscopy after autoxidation in slightly alkaline solutions were only partially identified due to their instability and generally represented dissociated O 4 -semiquinones. Hybrid density-functional calculations of the potential radical structures showed distinct differences between the resonance stabilization of the O 4 -and O 3 -semiquinones of caffeic and dihydrocaffeic acids, reflected also in the considerably faster decay of the O 3 -semiquinone observed by pulse radiolysis. No evidence was found for dimerization reactions via Cβ radicals typical for lignin biosynthesis.

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Unusually large numbers of electrons for the oxidation of polyphenolic antioxidants

Cited by 151 publications

References 55 publications

CYP98A3 from Arabidopsis thaliana Is a 3′-Hydroxylase of Phenolic Esters, a Missing Link in the Phenylpropanoid Pathway

CYP98A3 from Arabidopsis thaliana Is a 3′-Hydroxylase of Phenolic Esters, a Missing Link in the Phenylpropanoid Pathway

Enhancing Effect of Zinc on Hepatoprotectivity of Epigallocatechin Gallate in Isolated Rat Hepatocytes.

Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

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