Partial Purification and Properties of S-Adenosylmethionine: (R), (S)-Norlaudanosoline-6-O-Methyltransferase from Argemone platyceras Cell Cultures

Abstract

A new enzyme, S-adenosylmethionine: (R), (S)-norlaudanosoline-6-O-methyltransferase, was isolated from the soluble protein extract of A. platyceras cell cultures and purified approximately 80-fold. This enzyme catalyses the formation of 6-O-methylnorlaudanosoline, and, to a minor extent, 7-O-methylnorlaudanosoline from SAM and (S), as well as (R), norlaudanosoline. The apparent molcular weight of the enzyme is 47000 Dalton. The pH-optimum of the enzyme is 7.5, the temperature optimum, 35° C. Apparent K_M values for (S) and (R)-norlaudanosoline were 0.2 mM, and for SAM, 0.05 mM. The transferase shows high substrate specificity for tetrahydrobenzylisoquinoline alkaloids. Simple orthophenols, like phenylpropane derivatives, coumarins or flavonoids, are not accepted as substrates. The enzyme is widely distributed in benzylisoquinoline-containing plant cell cultures and is present in differentiated plants like Papaver somniferum.