Isoquinoline alkaloids, biosynthesis

In summary, the de novo isolation of the cDNAs encoding enzymes of alkaloid biosynthesis is still achieved by using a variety of classical techniques, such as protein purification followed by partial amino acid sequence determination, and by newer techniques such as proteomics coupled to functional heterologous expression. The current status of cloned cDNAs specifically related to isoquinoline alkaloid biosynthesis is schematically presented in Figure 10.8. New additions to this list will certainly be made in the future as a result of a combination of approaches both new and old. 

MORISHIGE, T TSUJITA, T YAMADA, Y SATO, F., Molecular characterization of the S-adenosyl-L-methionine 3 -hydroxy-A-methylcoclaurine 4 -0-methyltransferase involved in isoquinoline alkaloid biosynthesis in Coptis japonica, J. Biol. Chem., 2000, 275, 23398-23405. 

The role of reticuline as an intermediate in the biosynthesis of the mor-phinan alkaloids (Fig. 2.8) was demonstrated by the isolation both of (S)-and (f )-reticuline from the opium poppy. An excess of the (S)-reticuline over the (f )-isomer was found in opium (poppy latex) obtained from the mature plant, in contrast to the roughly equal amounts of these two isomers that occur in poppy seedlings. Both isomers were found to be incorporated into morphine, the major alkaloid isolated from opium, although incorporation of the (f )-isomer was slightly more efficient. (f )-Reticuline is firmly established in P. somniferum as the precursor of the morphinan-type alkaloids (Loefer and Zenk, 1990). (S)-Reticuline, however, is the central intermediate in isoquinoline alkaloid biosynthesis. It has been postulated that (R)-reticuline is formed from (S)-reticuline by isomerization. This inversion of configuration can be explained by the intermediate formation of the 1,2-dehydroreticulinium ion originating from (S)-reticuline, followed by stereospecific reduction to yield the (R) counterpart. The 1,2-dehydroreticulinium ion is efficiently incorporated into opium alkaloids and its role as a precursor of the morphinan-t)q)e alkaloids has been unequivocally established (De-Eknamkul and Zenk, 1990, 1992). 

The partial ether cleavage of methoxy- and methylenedioxy-substituted isoquinoline alkaloids has been reviewed in a new journal. Additional reviews concerning the use of Reissert compounds in the total synthesis of isoquinoline alkaloids and related compounds, electro-oxidation and isoquinoline alkaloid biosynthesis, and the synthesis of isoquinoline alkaloids by a systematic design have appeared in early issues of the same journal. The chemotaxonomy of alkaloids, together with distribution within plants, biosynthesis, structural classification, and physiological activity, has been treated in a monograph. ... 

Ikezawa N, Iwasa K, Sato F (2009) CYP719A subfamily of cytochrome P450 oxygenases and isoquinoline alkaloid biosynthesis in Eschscholzia caltfomica. Plant Cell Rep 28 123-133... 

Figure 3. Phenol Coupling in Isoquinoline Alkaloid Biosynthesis...

Isoquinoline alkaloid biosynthesis is one of the well-characterized pathways in the secondary metabolism of plant cells which comprises some of the most important drugs for therapy and euphoria (e.g., morphine and its chemical derivatives, papaverine, berberine, dimeric bisbenzylisoquinolines). 

Fig. 15.3 Isoquinoline alkaloid biosynthesis pathway represented in DbALBioPath database (Available at intranet, CSIR-CIMAP, Lucknow, India)...

Table 15.4 Predicted orthologs of isoquinoline alkaloid biosynthesis pathway enzymes (benzylisoquinoline) in other plants ...

Table 15.5 Details of enzymes detected for oithologs in other plants related to isoquinoline alkaloid biosynthesis pathway ...

Pathway Isoquinoline alkaloid biosynthesis (m00950), metabolic pathways (mOl 100),... 

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