Isolation and characterization of a novel O-methyltransferase from the tropical liana Triphyophyllum peltatum

The 'part-time' carnivorous plant [1] Triphyophyllum peltatum (Dioncophyllaceae) produces a large variety of naphthoquinones and naphthylisoquinoline alkaloids. These secondary metabolites show promising bioactivities [2] such as antimalarial and antitumoral effects. O-methylations are important steps in the biosynthetic pathway of these natural products. Our aim was to investigate involved O-methyltransferases (OMTs).

In the course of an expressed sequence tag analysis of shoot cultures of Triphyophyllum peltatum, several partial sequences of putative OMTs were found. One of these sequences, TpOMT1, was completed by RACE-PCR and the full-length cDNA was expressed in E. coli. A cladistic analysis identified the isolated OMT as a member of group II S-adenosyl-l-methionine-dependent OMTs. It is currently unknown in which metabolic pathways the isolated OMT is involved since it does not methylate the examined precursor naphthoquinones and naphthylisoquinoline alkaloids. Instead, caffeic acid, which is a key component of plant metabolism, as well as orcinol and resorcinol are methylated by the newly discovered OMT.

[1] Bringmann G, Schlauer J, Wolf K, Rischer H, Buschbom U, Kreiner A, Thiele F, Duschek M, Aké Assi L. Carniv Pl Newsl 1999; 28: 7 – 13

[2] Ibrahim SR, Mohamed GA. Fitoterapia 2015; 106: 194 – 225