Norcoclaurine synthase

Fig. 18 Reconstructed isoquinoline alkaloid biosynthetic pathway in microbes (E. coli and S. cerevisiae) [120]. Accession numbers of the genes can be taken from Gene Bank. C3,4-DHPA-A 3,4-dihydroxyphenylacetaldehyde NCS norcoclaurine synthase 60MT 6-0-methyltransferase CNMT coclaurine-/V-mcthyltransferase 4 OMT 4 -0-methyltransferase BBE berberine bridge enzyme NMT /V-methyltransferase)...

Figure 7.8 Schematic representation of the putative reaction mechanism for norcoclaurine synthase. A. 4-Hydroxyphenyl-acetaldehyde (black circles) binds to the enzyme. B. The binding of dopamine (gray squares) to one subunit of the enzyme increases the dopamine binding affinity of the second subunit. C. A second molecule of dopamine binds to the enzyme. The enzyme undergoes a conformational change (dark gray) during the reaction. D. The product, (5)-norcoclaurine, is released. E. The enzyme reverts to a conformation to which 4-HPAA can bind. F. A new reaction sequence begins.

SAMANANI, N., FACCHINI, P.J., Isolation and partial characterization of norcoclaurine synthase, the first committed step in benzylisoquinoline alkaloid biosynthesis, from opium poppy. Planta, 2001,213, 898-906. 

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

Condensation of dopamine and p-hydroxyphenylacetaldehyde is catalyzed by norcoclaurine synthase to form (S)-norcoclaurine (Fig. lb). Two norcoclaurine synthases with completely unrelated sequences were cloned (Thalictrum flavum and C. japon-ica) and heterologously expressed in E. coli (12-14). One is homologous to iron-dependent diooxygenases, whereas the other... 

The later steps of morphine biosynthesis have been investigated in P. somniferum cells and tissue. Notably, in morphine biosynthesis, (S)-reticuline is converted to (R)-reticuline, thereby epimerizing the stereocenter generated by norcoclaurine synthase at the start of the pathway (Fig. Id). (S)-reticuline is converted to (R)-reticuline through a 1,2-dehydroreticuline intermediate. Dehydroreticuline synthase catalyzes the oxidation of (S)-reticuline to 1,2-dehydroreticulinium ion (44). This enzyme has not been cloned but has been purified partially and shown to be membrane-associated. This intermediate then is reduced by dehydroreticuline reductase, an NADPH-dependent enzyme that stereoselectively transfers a hydride to dehydroreti-culinium ion to yield (R)-reticuline. This enzyme has not been cloned yet but has been purified to homogeneity (45). 

Samanani N, Facchini PJ. Purification and characterization of norcoclaurine synthase. J. Biol. Chem. 2002 277 33878-33883. 

Samanani N, Liscombe DK, Facchini PJ. Molecular cloning and characterization of norcoclaurine synthase, an enzyme catalyzing benzyUsoquinoline alkaloid biosynthesis. Plant J. 2004 40 302-313. 

Minami H, Dubouzet E, Iwasa K, Sato F. Functional analysis of norcoclaurine synthase in Coptis japonica. J. Biol. Chem. 2007 282 6274-6282. 

An aldehyde, 4-hydroxy-phenylacetaldehyde, operating under the influence of the enzyme norcoclaurine synthase, condenses with dopamine to afford (5)-nor-coclaurine, the progenitor of all benzylisoquinoline... 

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,...

Luk, L. Y., et al.. Mechanistic studies on norcoclaurine synthase of benzylisoquinoline alkaloid biosynthesis an enzymatic Pictet-Spengler reaction. Biochemistry, 2007. 46(35) p. 10153-61. 

Bonamore, A., et al., Norcoclaurine synthase mechanism of an enantioselective pictet-spengler catalyzing enzyme. Molecules, 2010. 15(4) p. 2070-8. 

Pasquo, A., et al.. Cloning, expression, crystallization and preliminary X-ray data analysis of norcoclaurine synthase from Thalictrum flavmn. Acta. Crystallogr. Sect. F. Struct. Biol Cryst. Commun., 2008. 64(Pt4) p. 281-3. 

The first step of this biosynthetic sequence involves conversion of the amine and aldehyde to (S)-norcoclaurine (23) with (S)-norcoclaurine synthase. This condensation is fol-... 

Scheme 13.40. A representation of the formation of (5 )-norcoclaurine by a combination of dopamine [3,4-dihydroxyphenethylamine, 2-(3,4-dihydroxyphenyl)ethanamine] with 4-hydroxyphenylacetaldehyde [2-(4-hydroxyphenyl)acetaldehyde] in the presence of (5 )-norcoclaurine synthase (EC 4.2.1.78). EC numbers and some graphic materials provided in this scheme have been taken from appropriate Unks in a URL starting with http // www.chem.qmul.ac.uk/iubmb/enzyme/.

It is interesting to note that, using complementary DNA (cDNA) (Chapter 14), that is, DNA obtained by synthesis from a messenger RNA (mRNA) template in a reaction catalyzed by reverse transcriptase enzyme, the norcoclaurine synthase enzyme has been characterized, and the pathway from the precursors has been shown to most likely involve imine formation and then cyclization in a process resembling the Pictet-Spengler reaction. ... 

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