S-adenosyl-l-methionine:trans-caffeoyl-coenzyme A 3-O-methyltransferase from elicitor-treated parsley cell suspension cultures

Abstract An S -adenosyl- l -methionine:caffeoyl-CoA 3- O -methyltransferase was purified 82-fold from elicitor-induced parsley cell suspension cultures by ammonium sulfate fractionation, anionic exchange and hydrophobic interaction chromatographies, and chromatofocusing. The enzyme has an apparent p I of 5.7 and a molecular weight of approx 48,000 determined by gel filtration chromatography. Maximal activity was observed at pH 7.5 in 50 m m phosphate or Tris-HCl buffers and the additional presence of 0.5 m NaCl. The methyltransferase activity was dependent on Mg 2+ , whereas EDTA, Mn 2+ , and Ca 2+ inhibited the reaction. The partially purified enzyme efficiently catalyzed the methylation of caffeoyl-CoA, but also accepted with low affinity various other caffeic esters as substrates. Dark-grown parsley cells contained considerable methyltransferase activity which was nevertheless increased approx threefold within 12 h following the addition of a crude fungal elicitor to the cell suspensions. We propose that the O -methyltransferase activity is an important component in the rapid resistance response of the cells, which depends on the formation of cell wall-bound ferulic polymers.