Stylopine, biosynthesis

BAUER, W., ZENK, M.H., Two methylenedioxy bridge forming cytochrome P-450 dependent enzymes are involved in (5)-stylopine biosynthesis. Phytochemistry, 1991,30,2953-2961. 

Ikezawa, N., Iwasa, K. and Sato, F. (2007) Molecular cloning and characterisation of methylenedioxy brifge-forming enzymes involved in stylopine biosynthesis in Eschscholzia californica. FEES., 274, 1019-1035. 

Ikezawa N, Iwasa K, Sato F. Molecular cloning and characterization of methylenedioxy bridge-forming enzymes involved in stylopine biosynthesis in E. californica. FEES J. 2007 274 1019-1035. 

The probability63 that (69) lies along the pathway to protoberberine and derived alkaloids, between scoulerine (65) and stylopine (70), has been supported by the observation that tritiated (69) is a precursor for protopine (73), and also for corynoline (78).64 Evidence previously obtained for the intermediacy of the metho-salt of stylopine [as (71)] in the biosynthesis of chelidonine (62)63 and protopine (73)63,65 has been affirmed, and it is apparently the a-form (71) and not the /3-form that is involved. [The authors are mistaken in assuming that ( —)-stylopine has the R-configuration at C-14 cf. ref. 63]. 

Figure 2.7 Biosynthesis of protopine and the benzophenanthridine alkaloids. STS, stylopine synthase SNMT, stylopine N-methyltransferase DBOX, dihydrosanguinarine oxidase SanR, sanguinarine reductase.

Stylopine, Chelidonine, and Related Alkaloids.—Full details have been published on a study of the biosynthesis of stylopine (71) and chelidonine (76) in Chelidonium majus. The original publications predate these reports so it is fitting that the work be summarized here. In any case some of the results are new and the work is notable for the rigour of its approach and the elegant application of tritium labelling as a probe for the course of the reactions involved. The results obtained with the R and S isomers of multiple labelled reticuline [as (67)] and scoulerine [as (68)] establish the biosynthetic sequence as (67) -> (68) (71) - (76) (-)-(5)-scoulerine was shown... 

Tani and Tagahara also studied the biosynthesis of rhoeadine and reported that in P. rhoeas this alkaloid arises from a-stylopine methochloride (58n) via protopine. jS-Stylopine methochloride does not participate in this biosynthesis (740). 

The biosynthesis proceeds from reticuline via proto-betberine derivatives, e.g., stylopine methochloride. lit. Mothes etal., p. 226-230 Prog. Bot. 51, 113-133 (1980). 

The benzophenanthridine skeleton is encountered in approximately 30 alkaloids, principally of the family Papaveraceae (Cordell, 1978a). In contrast to the biosynthesis of protopine alkaloids, phenanthridine alkaloids are synthesized in the cytoplasm (Hartmann, 1991). This type of system arises from a protoberberine precursor by fission of the C-6-N bond and recyclization. The biogenetic sequence leading to chelidonine (80) biosynthesis in Chelidonium majus has been supported by feeding experiments with multiply-labeled (-t-)-reticuline [(5)-reticuline] (20) and with labeled stylopine (79) (Fig. 32.25) (Hutchinson, 1986 Sim ek, 1985 Tanahashi and Zenk, 1988). (5)-Z-V-Methylstylopine and protopine (60) have been shown to be metabolites in this pathway. Reticuline is oxidatively cyclized to ( —)-scoulerine (72). Formation of two methylenedioxy groups results in the formation of stylopine (79) (Hartmann, 1991). 

In a study of the biosynthesis of stylopine in Chelidonium majus L. (Papaveraceae), labeled ( + )-reticuline was found to be converted first to (—)-scoulerine and then to (-)-stylopine in addition, no loss of label occurred in the conversion to ( —)-stylopine when the reticuline was tritiated at the C-1 position. 

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...

Battersby AR, Sheldrake PW, Milner JA (1974) Biosynthesis of colchicine Incorporation of a C4abelled precursor in a higher plant. Tetrahedron Lett 3315 -3318 Battersby AR, Francis RJ, Hirst M, Ruveda EA, Staunton J (1975) Biosynthesis, part XXL Investigations on the biosynthesis of stylopine in Chelidonium majus. J Chem Soc Perkin Trans 1 1140-1147... 

A hypothetical explanation for this could be, that berberine with its positive charge is too polar to be accepted. Furthermore enzymatic experiments diowed (Steffens et al. 1984, Amann et al. 1984) that the last steps in the biosynthesis of berberine do not take place in the cytosol and therefore probably no permeation processes would be necessary for the transfer into the vacuole. Alkaloids like nicotine, morphine or vindoline, which do not occur naturally in Thalictmm, are not accumulated in the vacuoles, whereas stylopine, a tetrahydroprotoberberine like cana-dine, could penetrate the tonoplast, even though only to a small extent, which supports a very specific uptake system located in the vacuole membrane. 

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