Partial purification and properties of S-adenosyl-l-methionine: (S)-tetrahydroprotoberberinecis-N-methyltransferase from suspension-cultured cells of Eschscholtzia and Corydalis

Abstract An enzyme has been found in different species of isoquinoline alkaloid-producing plant cell cultures which specifically N -methylates certain ( S )-tetrahydroprotoberberine alkaloids such as ( S )-canadine and ( S )-stylopine at the expense of S -adenosyl- l -methionine (SAM). It was partially purified (90-fold from Eschscholtzia californica cell suspension cultures and characterized. The enzyme has a pH optimum of 8.9, a temperature optimum at 40° and a M r of about 78 000 ± 10%. The K m for ( S )-canadine was determined to be 6.4,μM, for ( S )-stylopine 3.1 μM and for SAM 12,μM. The enzyme is inhibited by S -adenosyl- l -homocysteine (SAH with a K i of 24 μM.