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Cations modulate the substrate specificity of bifunctional class IO-methyltransferase fromAmmi majus

Authors
Journal
FEBS Letters
0014-5793
Publisher
Wiley Blackwell (John Wiley & Sons)
Publication Date
Volume
577
Issue
3
Identifiers
DOI: 10.1016/j.febslet.2004.10.032
Keywords
  • Lignin Biosynthesis
  • Caffeoyl Coenzyme-A Dependento-Methyltransferase
  • Substrate Specificity
  • Bivalent Cation
  • Ammi Majusl.
  • Apiaceae
Disciplines
  • Biology
  • Chemistry
  • Medicine

Abstract

Abstract Caffeoyl-coenzyme A O-methyltransferase cDNA was cloned from dark-grown Ammi majus L. (Apiaceae) cells treated with a crude fungal elicitor and the open reading frame was expressed in Escherichia coli. The translated polypeptide of 27.1-kDa shared significant identity to other members of this highly conserved class of proteins and was 98.8% identical to the corresponding O-methyltransferase from parsley. For biochemical characterization, the recombinant enzyme could be purified to apparent homogeneity by metal-affinity chromatography, although the recombinant enzyme did not contain any affinity tag. Based on sequence analysis and substrate specificity, the enzyme classifies as a cation-dependent O-methyltransferase with pronounced preference for caffeoyl coenzyme A, when assayed in the presence of Mg 2+-ions. Surprisingly, however, the substrate specificity changed dramatically, when Mg 2+ was replaced by Mn 2+ or Co 2+ in the assays. This effect could point to yet unknown functions and substrate specificities in situ and suggests promiscuous roles for the lignin specific cluster of plant O-methyltransferases.

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