The Methyltransferase Gene Superfamily: A Tree with Multiple Branches

Ibrahim, Ragai K.; Muzac, Ingrid

doi:10.1016/s0079-9920(00)80012-x

Cited by 35 publications

(23 citation statements)

References 65 publications

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“…In contrast to animal cells, plants are reported to contain several classes of OMTs involved in modification of phenolic compounds, with a clear cut difference in substrate preference (4). In this report we present several lines of evidence that methylation of flavonoid structures is not restricted to class II enzymes (4,25,48).…”

Section: Discussionmentioning

confidence: 65%

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A Novel Mg2+-dependent O-Methyltransferase in the Phenylpropanoid Metabolism of Mesembryanthemum crystallinum

Ibdah

Zhang

Schmidt

et al. 2003

Journal of Biological Chemistry

112

149

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Upon irradiation with elevated light intensities, the ice plant (Mesembryanthemum crystallinum) accumulates a complex pattern of methylated and glycosylated flavonol conjugates in the upper epidermal layer. Identification of a flavonol methylating activity, partial purification of the enzyme, and sequencing of the corresponding peptide fragments revealed a novel S-adenosyl-L-methionine-dependent O-methyltransferase that was specific for flavonoids and caffeoyl-CoA. Cloning and functional expression of the corresponding cDNA verified that the new methyltransferase is a multifunctional 26.6-kDa Mg 2؉ -dependent enzyme, which shows a significant sequence similarity to the cluster of caffeoyl coenzyme A-methylating enzymes. Functional analysis of highly homologous members from chickweed (Stellaria longipes), Arabidopsis thaliana, and tobacco (Nicotiana tabacum) demonstrated that the enzymes from the ice plant, chickweed, and A. thaliana possess a broader substrate specificity toward o-hydroquinone-like structures than previously anticipated for Mg 2؉ -dependent O-methyltransferases, and are distinctly different from the tobacco enzyme. Besides caffeoyl-CoA and flavonols, a high specificity was also observed for caffeoylglucose, a compound never before reported to be methylated by any plant O-methyltransferase. Based on phylogenetic analysis of the amino acid sequence and differences in acceptor specificities among both animal and plant Omethyltransferases, we propose that the enzymes from the Centrospermae, along with the predicted gene product from A. thaliana, form a novel subclass within the caffeoyl coenzyme A-dependent O-methyltransferases, with potential divergent functions not restricted to lignin monomer biosynthesis.Methylation by S-adenosyl-L-methionine (AdoMet) 1 dependent O-methyltransferases (OMTs) (EC 2.1.1) is a common modification in natural product biosynthesis. Site-specific O-methylation modulates the physiological properties of such compounds and reduces the chemical reactivity of phenolic hydroxyl groups (1). In plants, O-methylation is also required for monolignol biosynthesis and accounts for the structural differences and properties of lignin, which next to cellulose is the most prominent polymer on earth (2).Plant OMTs can be categorized into two major classes (3). Class I includes a group of low molecular weight (23,000 to 27,000) and Mg 2ϩ -dependent OMTs, whereas class II consists of higher molecular weight OMTs of about 38,000 to 43,000 that do not require Mg 2ϩ for catalytic activity. Prominent class II members include caffeic acid, flavonoid, coumarin, and alkaloid OMTs (4 -6). Within the class I OMTs, a group of small caffeoyl coenzyme A OMTs (CCoAOMTs) have been suggested to be key enzymes in the biosynthesis of monolignols, the precursors of gymnosperm and angiosperm lignins (7,8). In angiosperms, this task may also be performed by class II OMTs that are specific for caffeic acid, caffeyl aldehyde, or caffeyl alcohol (COMT) (9 -11). This apparent redundancy results in a cell-and tis...

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Section: Discussionmentioning

confidence: 65%

“…In this report we present several lines of evidence that methylation of flavonoid structures is not restricted to class II enzymes (4,25,48). The cation-dependent class I enzymes, the so-called "caffeoyl CoA-specific enzymes," also methylate other o-hydroquinone structures.…”

Section: Discussionmentioning

confidence: 84%

A Novel Mg2+-dependent O-Methyltransferase in the Phenylpropanoid Metabolism of Mesembryanthemum crystallinum

Ibdah

Zhang

Schmidt

et al. 2003

Journal of Biological Chemistry

112

149

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“…N-methyltransferases involved in BIA biosynthesis display substantial sequence similarity and catalyze the transfer of a methyl group to the nitrogen on the isoquinoline ring. Despite the occurrence of a similar S-adenosylmethionine binding domain, it is still not known whether O-and N-methyltransferases have a common ancestor (Ibrahim and Muzac 2000).…”

Section: Biosynthesis Of the Major Alkaloids In Opium Poppymentioning

confidence: 99%

Benzylisoquinoline alkaloid biosynthesis in opium poppy

Beaudoin

Facchini

2014

Planta

209

161

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“…It reduces the reactivity/mutagenicity of phenolic hydroxyl groups (Zhu et al, 1994) and increases the lipophilicity of flavonoids and, hence, their antimicrobial activity. A number of flavonoid OMT genes have been cloned and their gene products biochemically characterized Ibrahim & Muzac, 2000;Lam et al, 2007 and refs. therein).…”

Section: Introductionmentioning

confidence: 99%

Characterization of TwoO.-Methyltransferase-like Genes in Barley and Maize

Zhou

Fukushi

Wollenweber

et al. 2008

Pharmaceutical Biology

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Tricin (3 ,5 -dimethoxy-5,7,4 -trihydroxyflavone) is a characteristic flavone constituent of cereal grain plants that is credited for a variety of potential health benefits to humans. We have characterized the flavone-specific O-methyltransferase genes of barley (Hordem vulgare L., Gramineae), HvOMT1, and maize (Zea mays L., Gramineae), ZmOMT1, whose gene products use the flavone tricetin (5,7,3 ,4 ,5 -pentahydroxyflavone) as the preferred substrate and give rise to its 3 ,5 -dimethyl derivative, tricin, as the major product. The fact that homologous enzymes catalyze the same reaction also in wheat and rice suggests the existence in cereal grain plants of a flavone-specific O-methyltransferase multigene family. The natural occurrence of tricin in most monocot species implies the widespread occurrence of this gene family. The pharmacological significance of tricin as a naturally occurring constituent with a potential use as a nutraceutical, and the application of metabolic engineering methods to obtain tricin-enriched cereal grain products, are discussed.

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The Methyltransferase Gene Superfamily: A Tree with Multiple Branches

Cited by 35 publications

References 65 publications

A Novel Mg2+-dependent O-Methyltransferase in the Phenylpropanoid Metabolism of Mesembryanthemum crystallinum

A Novel Mg2+-dependent O-Methyltransferase in the Phenylpropanoid Metabolism of Mesembryanthemum crystallinum

Benzylisoquinoline alkaloid biosynthesis in opium poppy

Characterization of TwoO.-Methyltransferase-like Genes in Barley and Maize

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