The biosynthesis of shikimate metabolites

Dewick, P. M.

doi:10.1039/np9850200495

Cited by 6 publications

(5 citation statements)

References 9 publications

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“…In enzyme preparations from acyanic flowers, the dihydroflavonol 4-reductase activity was demon- strated to catalyse stereospecific reduction of ( + )-dihydrokaempferol (94) to ( + )-3,4-cis-leucopelargonidin (97) in the presence of NADPH cofactor. ( + )-Dihydroquercetin ( 95) and ( + )-dihydromyricetin (96) were also reduced (in agreement with the anthocyanidin pattern in the flowers) and were, in fact, better substrates than dihydrokaempferol. NADH was a less satisfactory cofactor.…”

Section: Flavanones Dihydroflavonols Anthocyanidins and Leucoanthocya...supporting

confidence: 64%

The biosynthesis of shikimate metabolites

Dewick¹

1990

Nat. Prod. Rep.

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Section: Flavanones Dihydroflavonols Anthocyanidins and Leucoanthocya...supporting

confidence: 64%

The biosynthesis of shikimate metabolites

Dewick¹

1990

Nat. Prod. Rep.

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“…At this critical juncture in evolution, phenylalanine (tyrosine) became the portal entry of phenols into lignins, lignans, flavonoids, suberins, and proanthocyanidins. Vascular plants thus have a very high Phe/Tyr turnover, since ϳ30 -40% of all assimilated carbon in photosynthesis is of phenylpropanoid/ phenylpropanoid-acetate origin (1)(2)(3)(4)(5).…”

mentioning

confidence: 99%

Nitrogen Metabolism in Lignifying Pinus taeda Cell Cultures

Heerden¹,

Towers²,

Lewis

1996

Journal of Biological Chemistry

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The primary metabolic fate of phenylalanine, following its deamination in plants, is conscription of its carbon skeleton for lignin, suberin, flavonoid, and related metabolite formation. Since this accounts for ϳ30 -40% of all organic carbon, an effective means of recycling the liberated ammonium ion must be operative. In order to establish how this occurs, the uptake and metabolism of various N NMR, and gas chromatography-mass spectrometry analyses. It was found that the ammonium ion released during active phenylpropanoid metabolism was not made available for general amino acid/protein synthesis. Rather it was rapidly recycled back to regenerate phenylalanine, thereby providing an effective means of maintaining active phenylpropanoid metabolism with no additional nitrogen requirement. These results strongly suggest that, in lignifying cells, ammonium ion reassimilation is tightly compartmentalized.The successful colonization of land by vascular plants, from their aquatic forerunners, was in large measure due to elaboration of the phenylpropanoid/phenylpropanoid-acetate pathways. At this critical juncture in evolution, phenylalanine (tyrosine) became the portal entry of phenols into lignins, lignans, flavonoids, suberins, and proanthocyanidins. Vascular plants thus have a very high Phe/Tyr turnover, since ϳ30 -40% of all assimilated carbon in photosynthesis is of phenylpropanoid/ phenylpropanoid-acetate origin (1-5).Phenylpropanoid metabolism is not only a feature of normal development, but can also be induced. For example, when loblolly pine (Pinus taeda) cell suspension cultures are exposed to high levels of sucrose (6), there is an induction of lignin synthesis. Curiously, little attention has been paid to the issue of the relationship between phenylpropanoid and nitrogen metabolism (7). This is surprising since there are many indications from physiological studies of significant metabolic relations between nitrogen depletion and the build-up of aromatic compounds, e.g. Lotus pendunculatus produces flavolans under nitrogen-limiting conditions, but not when nitrogen is provided (8).Scrutiny of the prearomatic pathway, leading to Phe/Tyr, and subsequent phenylpropanoid/phenylpropanoid-acetate metabolism reveals some noteworthy features. First, prephenate accepts an amino group from glutamate via transamination, constituting the point whereby nitrogen is introduced (9 -15). Second, when Phe/Tyr are committed to phenylpropanoid metabolism, rather than to protein or alkaloid synthesis, nitrogen (as the ammonium ion) is immediately removed via the appropriate lyase reaction (16 -18) (Scheme 1). Third, for every mole of cinnamate (p-hydroxycinnamate) formed, an equimolar amount of ammonium ion is generated. Consequently, an efficient means of nitrogen recycling must exist within cells undergoing active phenylpropanoid metabolism, otherwise severe nitrogen deficiency would result. A possible mechanism for recycling is shown in Scheme 2, where the ammonium ion released during lysis is metabolized via glutamine synthet...

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“…This has been demonstrated at the enzymic level for the conversion of ( 105) into (106) during the biosynthesis of the glyceollins in soybean, where a cytochrome-P-450-dependent mono-oxygenase was implicated and the 6ahydroxyl was derived from molecular oxygen (see ref. 91). Fungal 6a-hydroxylation of ( -)-maackiain ( 1 02) by Ncvtriu haematococca similarly gives ( -)-6a-hydroxymaackiain ( 107) into which label was incorporated in the presence of 1 8 0 2 , but no labelling occurred if H,'*O was supplied instead.…”

Section: Isoflavonoidsmentioning

confidence: 99%

“…The stereochemistry of the process was studied by two groups of workers in 1984 (see ref. 91) who, unfortunately, presented conflicting data. It has now been confirmed, in further studies with Datura innoxia plants, that migration of the carboxyl group occurs with retention of configuration at the benzylic centre of phenylalanineg2 and that there is also migration of one of these benzylic hydrogens to form the methylene of tropic acid (Scheme 18).…”

Section: Tropic Acidmentioning

confidence: 99%

“…: Chalaurenol A full report on the isolation and structure elucidation of chalaurenol (92), a novel quinol ether metabolite that is obtained from incubating 2',4,4'-trihydroxychalcone (isoliquiritigenin) (62) with a peroxidase preparation from Amorpha fruticosa (see ref. 91), has been p u b 1 i ~h e d . l ~~ Whilst this compound is produced by the enzyme of A .…”

Section: Quinol Ethersmentioning

confidence: 99%

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