Canadine synthase

CYP719A1 (canadine synthase) [109] is responsible for (S)-tetrahydroberberine production, which is then enzymatically oxidised to berberine. 

RUEFFER, M., ZENK, M.H., Canadine synthase from Thalictrum tuberosum cell cultures catalyzes the formation of the methylenedioxy bridge in berberine synthesis. Phytochemistry, 1994, 36, 1219-1223. 

Figure 2.6 Biosynthesis of berberine from (5)-reticuline in Berberis species and Coptis japonica. BBE, berberine bridge enzyme SCMT, (5)-scoulerine-9-0-methyltransferase CAS, (5)-canadine synthase STOX, tetrahydroberberine oxidase COX, enzyme found in Coptis japonica.

The formation of the methylenedioxy bridge in Berberis has been found to be caused by the demethylating activity of a peroxidase (POD) found within the vesicle. It was also found that the cytochrome P450-requiring enzyme (canadine synthase) from microsomes of Berberis, Thalictrum and Coptis species formed the methylene bridge in (S)-tetrahydrocolumbamine (Ikezawa et al, 2003), but not in the quaternary alkaloid columbamine (Galneder et al, 1988 Zenk, 1995). Because of the substrate specificity of canadine s)mthase, the berberine pathway is considered to be that presented in Fig. 2.5 (Rueffer and Zenk, 1994). Columbamine, once proposed as an alternative route to berberine, is however converted to palmatine by a specific methyltransferase first isolated from Berberis wilsoniae cell cultures (Rueffer and Zenk, 1985 Ikezawa et al, 2003). 

Scheme 1. Biosynthesis of the benzylisoquinoline alkaloids berberine, morphine, and sang-uinarine. Enzymes for which corresponding molecular clones have been isolated are shown in bold. Abbreviations 4 OMT, 3 -hydroxy-A-methylcoclaurine 4 -0-methyltransferase 60MT, norcoclaurine 6-0-methyltransferase 70MT, reticuline 7-0-methyltransferase BBE, berberine bridge enzyme CFS, cheilanthifoline synthase CNMT, coclaurine A-methyltransf-erase COR, codeinone reductase CYP719A1, canadine synthase CYP80A1, berbamunine synthase CYP80B1, A-methylcoclaurine 3 -hydroxylase DBOX, dihydrobenzophenanthri-dine oxidase DRR, 1,2-dehydroreticuline reductase DRS, 1,2-dehydro reticuline synthase MSH, A-methylstylopine 14-hydroxylase NCS, norcoclaurine synthase P6H,...

A1 Canadine synthase Protoberberine and phthalideisoquin- oline alkaloids Berberine [80]... 

A21 Canadine synthase Phthalideisoquinoline alkaloids Noscapine [226]... 

ElO (S)-canadine synthase CYP, EcCYP Thalictrum flavum subsp. glaucum... 

Figure 4.2 Biosynthesis of benzylisoquinoline alkaloids. Enzyme abbreviations TYDC, tyrosine/dopa decarboxylase NCS, norcoclaurine synth lse 60MT, norcoclaurine 6-O-methyltransferase 4 OMT, 3 -hydroxy-/V-methylcoclaurine 4 -0-methyltransferase CYP80A, berbamunine synth lse CYP80B, N-methylcoclaurine 3 -hydroxylase BBE, berberine bridge enzyme SOMT, scoulerine 9-0-methyltransferase CYP719A, (S)-canadine synthase SAT, salutaridinol 7-O-acetyltransferase COR, codeinone reductase.

Scheme 11. Biosynthesis rfbeiherine based on in vivo experiments with Coptisjaponica (51). The enzymes involved in the process are 1-Beiberiiie bridge en m 2-(5)>Sooulerine-9 >m yl-tnmsferase 3 - Canadine synthase 4 - (SHeliai drabeiberine oxidase.

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