Reticuline oxidase

This enzyme [EC 1.5.3.9], also called reticuline oxidase and tetrahydroprotoberberine synthase, catalyzes the re-... 

Enzyme 1.14.21.4 salutaridine synthase (R)-reticuline oxidase (C-C phenol-... 

Reticuline is a chemical compound that can be found in Lindera aggregata. It is also one of the alkaloids found in opium. Metabolism showed that 3 -hydroxy-A -methyl-(S)-coclaurine 4 -0-methyltransferase uses 5-adenosyl methionine and 3 -hydroxy-A -methyl-(S)-coclaurine to produce S-adenosylhomocysteine and (S)-reticuline. Reticuline oxidase uses (S)-reticuline and O2 to produce (S)-scoulerine and H2O2. Salutaridine synthase uses (R)-reticuline, NADPH, H", and O2 to produce salutaridine, NADP", and H2O. 1,2-dehydroreticulinium reductase (NADPH) uses (R)-reticuline and NADP + to produce 1,2-dehydroreticulinium, NADPH, and H". ... 

Reticuline oxidase BBE berberine bridge enzyme berberine-bridge-forming enzyme tetrahydroprotoberberine synthase oxidoreductases Isoquinoline alkaloid biosynthesis (m00950)... 

FIGURE 2. Alignment of the deduced amino acid sequences of GLO, 6-hydroxy-D-nicotine oxidase (6-HDNO), mcrA protein (MCRA), and berberine bridge enzyme (reticuline oxidase) (BBE). Identical residues are boxed. Arrowhead indicates the position of the histidyl residue to which FAD is covalently bound in 6-hydroxy-D-nicotine oxidase. Adapted from Brandsch (1994) and August et al. (1994). 

Fig. 10.3 Reaction catalyzed by the cytochrome P-450-dependent oxidase berbamunine synthase (CYP80A1). This enzyme creates a branchpoint in the (5)-reticuline biosynthetic pathway to form the bisbenzylisoquinoline alkaloids.

Fig. 17 Sequential enzymatic formation of berberine from (S)-reticuline (BBE berberine bridge enzyme SOMT scoulerine O-methyltransferase THCOX tetrahydrocolumbamine oxidase COX columbamine oxidase)...

In a remarkable approach involving both microbial and plant genes, reticuline was produced by transgenic E. coli (Fig. 18) [120]. This resulting strain, expressing the cDNAs of the five enzymes monoamine oxidase (MAO) from Micrococcus... 

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 conversion of (S)-reticuline to 1,2-dehydroreticuline has been accomplished using a novel oxidase isolated from cell cultures of plants of the... 

Based on knowledge of a biosynthetic pathway one can select certain steps which could be of interest for bioconversion of (a) readily available precursor(s). This could, for example, be stereospecific reactions, like the reduction of quinidinone in quinine or quinidine and the epoxidation of atropine to scopolamine. For the bioconversion one can consider using plant cells [e.g., the production of L-dopa from tyrosine by immobilized cells of Mucuna pruriens (10)] or isolated enzymes from the plant itself. An interesting example of the latter is the (5)-tetrahydroprotoberberine oxidase (STOX) enzyme, which oxidizes (5)-reticuline but not its stereoisomer (11). This feature can be used in the production of (i )-reticuline from a racemic mixture (see below). Immobilized strictosidine synthase has been successfully used to couple secologanin and tryptamine. The gene for this enzyme has been isolated from Rauvolfia (6) and cloned in Escherichia coli, in which it is expressed, resulting in the biosynthesis of active enzyme (7). The cultured bacteria produced 20 times more enzyme... 

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,...

The first reaction in the direction of the protoberberines is the formation of the berberine bridge (Fig. 2), catalyzed by the berberine bridge enzyme (abbreviated BBE), which specifically only accepts (S)-reticuline and not the (R)-enantiomer as substrate (ref. 23). As a next step a methylation at C-9 follows to form (S)-tetrahydrocolumbamine catalyzed by a methyltransferase with a much higher substrate specificity than the methyltransferases described before (ref. 24). In the genus Berberis (S)-tetrahydrocolumbamine is then oxidized by an enzyme called (S)-tetrahydroprotoberberine oxidase (abbreviated STOX) (ref. 25) and finally the methylene dioxy bridge is formed by the so called berberine synthase (ref. 26). 

Alkaloids of the morphinane group. If the tetrahydroisoquinoline alkaloid norlaudanosoline is written in such a way that part of the molecule is rotated around the dotted line (Fig. 280), the relationship to the morphinane-type alkaloids becomes obviously. The actual precursor of these compounds, however, is (R)-reticuline. It is probably attacked by a phenol oxidase (C 2.3.1) yielding a biradical which is stabilized by the formation of the dienone (- -)-salutaridine. After reduction of (-j-)-salutaridine closure of a new 0-heterocyclic ring results in the formation of thebaine. The alkaloids codeine and morphine are synthesized from thebaine in Papaver somniferum,... 

The bacterium E. coli and yeast S. cerevisiae have been recently explored as production hosts of plant alkaloids [15, 101, 102]. In both cases, the metabolic engineering efforts in microorganisms entailed the reconstmction of the plant biosynthetic pathways (Fig. 8.12) [101]. To assemble an artificial pathway to achieve (S)-reticuline biosynthesis in E. coli. Micrococcus luteus monoamine oxidase (MAO) was introduced together with Coptis japonica norcoclaurine... 

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