Purification and properties of caffeic acid O-methyltransferase from alfalfa root nodules

Abstract An O -methyltransferase which catalyses the methylation of caffeic acid to ferulic acid using S -adenosyl- l -methionine as methyl donor has been isolated and purified ca 70-fold from root nodules of alfalfa. The enzyme also catalysed the methylation of 5-hydroxyferulic acid. Chromatography on 1,6-diaminohexane agarose (AH-Sepharose-4B) linked with S -adenosyl- l -homocysteine (SAH) gave 35% recovery of enzyme activity. The K m values for caffeic acid and S -adenosyl- l -methionine were 58 and 4.1 μM, respectively. S -Adenosyl- l -homocysteine was a potent competitive inhibitor of S -adenosyl- l -methionine with a K i of 0.44 μM. The MW of the enzyme was ca 103 000 determined by gel filtration chromatography.