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KMID : 0368420110540050314
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Journal of Plant Biology
2011 Volume.54 No. 5 p.314 ~ p.314
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Characterization of Phenylpropanoid O-Methyltransferase from Rice: Molecular Basis for the Different Reactivity Toward Different Substrates
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Sung Su-Hyun
Kim Bong-Gyu
Chong You-Hoon
Ahn Joong-Hoon
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Abstract
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O-Methyltransferases (OMTs) transfer a methyl group from S-adenosylmethionine to a hydroxyl group of an acceptor. One group of OMTs is the caffeoyl-CoA O-methyltransferase type, which is involved in the biosynthesis of monolignol. In this study, OsOMT26 was cloned from Oryza sativa and the recombinant OsOMT26 protein was characterized. OsOMT26 used not only caffeoyl-CoA as a substrate but also different flavonoids such as luteolin and tricetin. However, when caffeoyl-CoA was used as the substrate, the reactivity of OsOMT26 was approximately 6.6-fold better than when either luteolin or tricetin was used. This result demonstrated that OsOMT26 displayed the typical properties characteristic of CCoAOMT. Molecular modeling followed by site-directed mutagenesis was employed to examine why caffeic acid or caffeoyl-CoA was a better substrate than tricetin. One amino acid, Asp210, turned out to be critical for substrate binding, and site-directed mutagenesis of Asp to Glu improved the enzyme’s reactivity toward tricetin.
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KEYWORD
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O-Methyltransferase, Molecular modeling, Oryza sativa, Phenylpropanoid
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