Coclaurine N methyltransferase

Figure 2.5 Formation of (5)-reticuline. NCS, norcoclaurine synthase 60MT, 6-hydroxy-O-methyltransferase CNMT, coclaurine N-methyltransferase 40MT, 4 hydroxy-0-methyltransferase.

Choi, K.-B., Morishige, T., Shitan, N., Yazaki, K. and Sato, F. (2002) Molecular cloning and characterization of coclaurine N-methyltransferase from cultured cells of Coptis japonica. J. Biol. Chem. 277, 830-35. 

Morishige T, Qioi KB, Sato F (2004) In vivo bioconversion of tetrahydroisoquinoline by recombinant coclaurine N-methyltransferase. Biosci Biotechnol Biochem 68 939-941... 

Fig. 4 Pathways of benzylisoquinoline biosynthesis. A selection of biosynthetic enzymes is notified with their localization in the cytosol (yellow), the ER membrane (red) or in the lumen of cytosolic vesicles (blue). Informations are taken mainly from Facchini and St-Pierre (2005), Bock et al. (2002), own experiments and other references cited in the text. BBE, berberine bridge enzyme CFS, cheilanthifoline synthase CNMT, coclaurine N-methyltransferase COR, codeinone reductase DBOX, dihydrobenzophen-anthridine oxidase MSH, N-methylstylopine 14-hydroxylase NCS, norcoclaurine synthase NMCH, N-methylcoclaurme 3 -hydroxylase 4 OMT, 3 -hydroxy-N-methylcoclaurine 4 -0-methyltransferase 60MT, norcoclaurine 6-O-methyltransferase 70MT, reticuline 7-O-methyltransferase P6H, protopine 6-hydroxylase SAT, salutaridinol-7-O-acetyltransferase SOR, salutaridineiNADPH 7-oxidoreductase STS, stylopine synthase SAS, salutaridine synthase TNMT, tetrahydroprotoberberine cis-N-methyltrans-ferase TYDC, tyrosine decarboxylase CAS, canadine sjmthase SOMT, scoulerine 9-O-methyltransferase STOX, (S)-tetrahydroprotoberberine oxidase...

FRENZEL, T., ZENK, M.H., S-Adenosyl-L-methionine 3 -hydroxy-N-methyl-(stereoselective enzyme of the (S)-reticuline pathway. Phytochemistry, 1990,29,3505-3511. 

The three steps of methylation of norlaudanosoline (iii, iv, v) are catalyzed by three kinds of methyltransferases (60MT, CNMT, and 4 OMT). These enzymes need 5-adenosyl-L-methionine (SAM) as the methyl donor. The 60MT and CNMT from C. japonica have broad substrate selectivity. Therefore, 60MT can catalyze the 6-(9-methlyation of not only norcoclaurine (VI) but also norlaudanosoline (iii). Similarly, CNMT can catalyze the N-methylation of not only coclaurine (VII) but also 6-(9-methylnorlaudanosoline (iv). 

---