Molecular cloning and heterologous expression of a cDNA encoding berbamunine synthase, a C--O phenol-coupling cytochrome P450 from the higher plant Berberis stolonifera

Identification of the cytochrome P450s responsible for the biosynthesis of two types of aporphine alkaloids and their de novo biosynthesis in yeast

Aporphine alkaloids have diverse pharmacological activities; however, our understanding of their biosynthesis is relatively limited. Previous studies have classified aporphine alkaloids into two categories based on the configuration and number of substituents of the D-ring and have proposed preliminary biosynthetic pathways for each category. In this study, we identified two specific cytochrome P450 enzymes (CYP80G6 and CYP80Q5) with distinct activities toward (S)-configured and (R)-configured substrates from the herbaceous perennial vine Stephania tetrandra, shedding light on the biosynthetic mechanisms and stereochemical features of these two aporphine alkaloid categories. Additionally, we characterized two CYP719C enzymes (CYP719C3 and CYP719C4) that catalyzed the formation of the methylenedioxy bridge, an essential pharmacophoric group, on the A- and D-rings, respectively, of aporphine alkaloids. Leveraging the functional characterization of these crucial cytochrome P450 enzymes, we reconstructed the biosynthetic pathways for the two types of aporphine alkaloids in budding yeast (Saccharomyces cerevisiae) for the de novo production of compounds such as (R)-glaziovine, (S)-glaziovine, and magnoflorine. This study provides key insight into the biosynthesis of aporphine alkaloids and lays a foundation for producing these valuable compounds through synthetic biology.

The CYP80A and CYP80G Are Involved in the Biosynthesis of Benzylisoquinoline Alkaloids in the Sacred Lotus (Nelumbo nucifera)

Bisbenzylisoquinoline and aporphine alkaloids are the two main pharmacological compounds in the ancient sacred lotus (Nelumbo nucifera). The biosynthesis of bisbenzylisoquinoline and aporphine alkaloids has attracted extensive attention because bisbenzylisoquinoline alkaloids have been reported as potential therapeutic agents for COVID-19. Our study showed that NnCYP80A can catalyze C-O coupling in both (R)-N-methylcoclaurine and (S)-N-methylcoclaurine to produce bisbenzylisoquinoline alkaloids with three different linkages. In addition, NnCYP80G catalyzed C-C coupling in aporphine alkaloids with extensive substrate selectivity, specifically using (R)-N-methylcoclaurine, (S)-N-methylcoclaurine, coclaurine and reticuline as substrates, but the synthesis of C-ring alkaloids without hydroxyl groups in the lotus remains to be elucidated. The key residues of NnCYP80G were also studied using the 3D structure of the protein predicted using Alphafold 2, and six key amino acids (G39, G69, A211, P288, R425 and C427) were identified. The R425A mutation significantly decreased the catalysis of (R)-N-methylcoclaurine and coclaurine inactivation, which might play important role in the biosynthesis of alkaloids with new configurations.

Alkylphenols disrupt estrogen homeostasis via diradical cross-coupling reactions: A novel pathway of endocrine disruption

Estrogen, being an essential class of sex hormone, is an important target of endocrine disruption chemicals. It is well known that environmental disruptors could activate or inhibit estrogen receptors, acting as agonists or antagonists, and thus affect the circulating estrogen concentrations. Here, we report enzyme-mediated diradical cross-coupling reactions between alkylphenols (e.g., 2,4-di-tert-butylphenol [DBP], 4-nonylphenol [4-NP], and 4-tert-octylphenol [4-t-OP]) and estrogens (e.g., estradiol [E2]) that generate coupling metabolites and disrupt estrogen homeostasis. Among the phenolic xenobiotics, the screening of metabolic products revealed that alkylphenols had the highest reaction activities and generated coupling metabolites with high abundances (DBP-O-E2, 4-t-OP-O-E2, and 4-NP-O-E2). The coupling reactions were catalyzed by cytochrome P450 3A4 (CYP3A4) and verified by the detection of the coupling products in general populations. In vitro and in vivo exposures together with CYP3A4 inhibition demonstrated that cross-coupling reactions of phenols and E2 significantly reduced the normal levels of E2. We further established a unique spin-trapping-based high-throughput screening method to show the existence of diradicals in the coupling reaction. Density functional theory calculations revealed that spin aromatic delocalization was the fundamental cause of the high rebound barrier and sufficient lifetime of phenoxy radicals that enabled phenolic cross-coupling triggered by cytochrome P450. The identified mechanistic details for diradical cross-coupling reactions provide a novel pathway for phenolic chemicals to disrupt estrogen homeostasis.

Comparative transcriptome analysis of different tissues of Solanum khasianum reveals candidate genes involved in steroidal glycoalkaloid biosynthesis

Fruits and leaves of Solanum khasianum C. B. Clarke have long been used as a common Chinese herbal medicine. Steroidal glycoalkaloids (SGAs), the main active ingredient in S. khasianum, exhibit various pharmacological effects. However, genes involved in the SGA biosynthetic pathway in S. khasianum have not yet been identified. Genes encoding potential key SGA biosynthesis enzymes were identified through comprehensive RNA sequencing analysis (RNA-seq) of S. khasianum leaves, stems, and fruits. A total of 123,704 unigenes were obtained, of which 109,775 (88.74%) were annotated in seven public databases. Among these, 54 unigenes potentially involved in SGA biosynthesis were identified. Additionally, 23,636 differentially expressed genes were identified by comparing gene expression levels among the fruits, stems, and leaves of S. khasianum. The structural characteristics and phylogenetic relationship of cycloartenol synthase involved in SGA biosynthesis were further analyzed. Solasodine constituent was detected by high-performance liquid chromatography. This is the first study to report the comparative transcriptome analysis of different tissues of S. khasianum that identifies valuable genes potentially involved in SGA biosynthesis in this species.

Visualization and identification of benzylisoquinoline alkaloids in various nelumbo nucifera tissues

Benzylisoquinoline alkaloids in lotus (Nelumbo nucifera) seed plumules and leaves exhibit significant tissue specificity for their pharmacological effects and potential nutritional properties. Herein, 46 benzylisoquinoline alkaloids were identified via UPLC-QTOF-HRMS, of which 9 were annotated as glycosylated monobenzylisoquinoline alkaloids concentrated in the seed plumules. The spatial distribution of targeted benzylisoquinoline alkaloids in leaves, seed plumules, and milky sap was determined via MALDI-MSI. Furthermore, 37 Nelumbo cultivars were investigated using targeted metabolomics to provide insights into functional tea development. While aporphine alkaloids comprised the main compounds present in lotus leaves, bisbenzylisoquinoline alkaloids were the main compounds in lotus plumules, where glycosylation primarily occurs. These findings can help understand the distribution of benzylisoquinoline alkaloids in lotus tissue and the directional breeding of varieties enriched with specific chemical functional groups for nutritional and pharmacological applications.

Elucidation of the (R)-enantiospecific benzylisoquinoline alkaloid biosynthetic pathways in sacred lotus (Nelumbo nucifera)

Benzylisoquinoline alkaloids (BIAs) are a structurally diverse group of plant specialized metabolites found mainly in members of the order Ranunculales, including opium poppy (Papaver somniferum), for which BIA biosynthetic pathways leading to the critical drugs morphine, noscapine, and sanguinarine have been elucidated. Sacred lotus (Nelumbo nucifera), in the order Proteales, accumulates medicinal BIAs in the proaporphine, aporphine, and bisbenzylisoquinoline structural subgroups with a prevalence of R enantiomers, opposed to the dominant S configuration occurring in the Ranunculales. Nevertheless, distinctive BIA biosynthetic routes in sacred lotus have not been explored. In planta labeling experiments and in vitro assays with recombinant enzymes and plant protein extracts showed that dopamine and 4-hydroxyphenylacetaldehyde derived from L-tyrosine serve as precursors for the formation of (R,S)-norcoclaurine in sacred lotus, whereas only (R)-norcoclaurine byproducts are favored in the plant by action of R-enantiospecific methyltransferases and cytochrome P450 oxidoreductases (CYPs). Enzymes responsible for the R-enantiospecific formation of proaporphine (NnCYP80Q1) and bisbenzylisoquinoline (NnCYP80Q2) scaffolds, and a methylenedioxy bridge introduction on aporphine substrates (NnCYP719A22) were identified, whereas additional aspects of the biosynthetic pathways leading to the distinctive alkaloid profile are discussed. This work expands the availability of molecular tools that can be deployed in synthetic biology platforms for the production of high-value alkaloids.

μ-Oxo-bis[(octacosafluoro-meso-tetraphenylporphyrinato)iron(iii)] - synthesis, crystal structure, and catalytic activity in oxidation reactions

We describe the synthesis and X-ray crystal structure of μ-oxo-bis[(octacosafluoro-meso-tetraphenylporphyrinato)iron(iii)] [(FeTPPF₂₈)₂O]. This novel iron complex is an efficient catalyst for oxidative biaryl coupling reactions of diarylamines and carbazoles. The asymmetric oxidative coupling in the presence of an axially chiral biaryl phosphoric acid as co-catalyst provides the 2,2'-bis(arylamino)-1,1'-biaryl in 96% ee. The Wacker-type oxidation of alkenes to the corresponding ketones with (FeTPPF₂₈)₂O as catalyst in the presence of phenylsilane proceeds at room temperature with air as the terminal oxidant. For internal and aliphatic alkenes increased ketone/alcohol product ratios were obtained.

Comparative Transcriptomics for Genes Related to Berberine and Berbamine Biosynthesis in Berberidaceae

Berberine and berbamine are bioactive compounds of benzylisoquinoline alkaloids (BIAs) present in Berberis species. The contents of berbamine are 20 times higher than berberine in leaf tissues in three closely related species: Berberis koreana, B. thunbergii and B. amurensis. This is the first report on the quantification of berberine compared to the berbamine in the Berberis species. Comparative transcriptome analyses were carried out with mRNAs from the leaf tissues of the three-species. The comparison of the transcriptomes of B. thunbergii and B. amurensis to those of B. koreana, B. thunbergii showed a consistently higher number of differentially expressed genes than B. amurensis in KEGG and DEG analyses. All genes encoding enzymes involved in berberine synthesis were identified and their expressions were variable among the three species. There was a single copy of CYP80A/berbamunine synthase in B. koreana. Methyltransferases and cytochrome P450 mono-oxidases (CYPs) are key enzymes for BIA biosynthesis. The current report contains the copy numbers and other genomic characteristics of the methyltransferases and CYPs in Berberis species. Thus, the contents of the current research are valuable for molecular characterization for the medicinal utilization of the Berberis species.

A Streptomyces P450 enzyme dimerizes isoflavones from plants

Dimerization is a widespread natural strategy that enables rapid structural diversification of natural products. However, our understanding of the dimerization enzymes involved in this biotransformation is still limited compared to the numerous reported dimeric natural products. Here, we report the characterization of three new isoflavone dimers from Streptomyces cattleya cultured on an isoflavone-containing agar plate. We further identified a cytochrome P450 monooxygenase, CYP158C1, which is able to catalyze the dimerization of isoflavones. CYP158C1 can also dimerize plant-derived polyketides, such as flavonoids and stilbenes. Our work represents a unique bacterial P450 that can dimerize plant polyphenols, which extends the insights into P450-mediated biaryl coupling reactions in biosynthesis.

Transcriptome Analysis of Stephania tetrandra and Characterization of Norcoclaurine-6-O-Methyltransferase Involved in Benzylisoquinoline Alkaloid Biosynthesis

Stephania tetrandra (S. Moore) is a source of traditional Chinese medicine that is widely used to treat rheumatism, rheumatoid arthritis, edema, and hypertension. Benzylisoquinoline alkaloids (BIAs) are the main bioactive compounds. However, the current understanding of the biosynthesis of BIAs in S. tetrandra is poor. Metabolite and transcriptomic analyses of the stem, leaf, xylem, and epidermis of S. tetrandra were performed to identify candidate genes associated with BIAs biosynthesis. According to the metabolite analysis, the majority of the BIAs accumulated in the root, especially in the epidermis. Transcriptome sequencing revealed a total of 113,338 unigenes that were generated by de novo assembly. Among them, 79,638 unigenes were successfully annotated, and 42 candidate structural genes associated with 15 steps of BIA biosynthesis identified. Additionally, a new (S)-norcoclaurine-6-O-methyltransferase (6OMT) gene was identified in S. tetrandra, named St6OMT2. Recombinant St6OMT2 catalyzed (S)-norcoclaurine methylation to form (S)-coclaurine in vitro. Maximum activity of St6OMT2 was determined at 30°C and pH 6.0 in NaAc-HAc buffer. Its half-life at 50°C was 22 min with the K_m and k_cat of 28.2 μM and 1.5 s^-1, respectively. Our results provide crucial transcriptome information for S. tetrandra, shedding light on the understanding of BIAs biosynthesis and further gene functional characterization.

Complete biosynthesis of the bisbenzylisoquinoline alkaloids guattegaumerine and berbamunine in yeast

This work demonstrates microbial biosynthesis of bisbenzylisoquinoline (bisBIA) alkaloids. We show that several didomain epimerases can function in yeast to epimerize the nonnative substrate N-methylcoclaurine, an essential step in bisBIA biosynthesis. The N-methylcoclaurine epimerase activity was increased 10-fold by combining individual reductase and oxidase domains from different plant species. Strain engineering and optimization of media and growth conditions increased the bisBIA titer over 10,000-fold. We show that strains can be engineered to primarily produce one bisBIA product by selection of the cytochrome P450 variant that couples the monomer BIA subunits. We then leverage our bisBIA biosynthetic strain as a platform for the screening of other plant enzymes to produce two additional plant natural products de novo in a heterologous host.

Benzylisoquinoline alkaloids (BIAs) are a diverse class of medicinal plant natural products. Nearly 500 dimeric bisbenzylisoquinoline alkaloids (bisBIAs), produced by the coupling of two BIA monomers, have been characterized and display a range of pharmacological properties, including anti-inflammatory, antitumor, and antiarrhythmic activities. In recent years, microbial platforms have been engineered to produce several classes of BIAs, which are rare or difficult to obtain from natural plant hosts, including protoberberines, morphinans, and phthalideisoquinolines. However, the heterologous biosyntheses of bisBIAs have thus far been largely unexplored. Here, we describe the engineering of yeast strains that produce the Type I bisBIAs guattegaumerine and berbamunine de novo. Through strain engineering, protein engineering, and optimization of growth conditions, a 10,000-fold improvement in the production of guattegaumerine, the major bisBIA pathway product, was observed. By replacing the cytochrome P450 used in the final coupling reaction with a chimeric variant, the product profile was inverted to instead produce solely berbamunine. Our highest titer engineered yeast strains produced 108 and 25 mg/L of guattegaumerine and berbamunine, respectively. Finally, the inclusion of two additional putative BIA biosynthesis enzymes, SiCNMT2 and NnOMT5, into our bisBIA biosynthetic strains enabled the production of two derivatives of bisBIA pathway intermediates de novo: magnocurarine and armepavine. The de novo heterologous biosyntheses of bisBIAs presented here provide the foundation for the production of additional medicinal bisBIAs in yeast.

An updated review on pharmacological properties of neferine-A bisbenzylisoquinoline alkaloid from Nelumbo nucifera

Phytochemicals have recently received a lot of recognition for their pharmacological activities such as anticancer, chemopreventive, and cardioprotective properties. In traditional Indian and Chinese medicine, parts of lotus (Nelumbo nucifera) such as lotus seeds, fruits, stamens, and leaves are used for treating various diseases. Neferine is a bisbenzylisoquinoline alkaloid, a major component from the seed embryos of N. nucifera. Neferine is effective in the treatment of high fevers and hyposomnia, as well as arrhythmia, platelet aggregation, occlusion, and obesity. Neferine has been found to have a variety of therapeutic effects such as anti-inflammatory, anti-oxidant, anti-hypertensive, anti-arrhythmic, anti-platelet, anti-thrombotic, anti-amnesic, and negative inotropic. Neferine also exhibited anti-anxiety effects, anti-cancerous, and chemosensitize to other anticancer drugs like doxorubicin, cisplatin, and taxol. Induction of apoptosis, autophagy, and cell cycle arrest are the key pathways that underlying the anticancer activity of neferine. Therefore, the present review summarizes the neferine biosynthesis, pharmacokinetics, and its effects in myocardium, cancer, chemosensitizing to cancer drug, central nervous system, diabetes, inflammation, and kidney diseases. PRACTICAL APPLICATIONS: Natural phytochemical is gaining medicinal importance for a variety of diseases like including cancer, neurodegenerative disorder, diabetes, and inflammation. Alkaloids and flavonoids, which are abundantly present in Nelumbo nucifera have many therapeutic applications. Neferine, a bisbenzylisoquinoline alkaloid from N. nucifera has many pharmacological properties. This present review was an attempt to compile an updated pharmacological action of neferine in different disease models in vitro and in vivo, as well as to summarize all the collective evidence on the therapeutic potential of neferine.

Functional characterization of (S)-N-methylcoclaurine 3'-hydroxylase (NMCH) involved in the biosynthesis of benzylisoquinoline alkaloids in Corydalis yanhusuo

Benzylisoquinoline alkaloids (BIAs) are compounds naturally found in plants and can have significant value in clinical settings. Metabolic engineering and synthetic biology are both promising approaches for the heterologous acquisition of benzylisoquinoline alkaloids. (S)-N-methylcoclaurine 3'-hydroxylase (NMCH), a member of the CYP80 family of CYP450, is the penultimate catalytic enzyme that forms the central branch-point intermediate (S)-reticuline and plays a key role in the biosynthesis of BIAs. In this study, an NMCH gene was cloned from Corydalis yanhusuo, while in vitro reactions demonstrated that CyNMCH can catalyze (S)-N-methylcoclaurine to produce (S)-3'-hydroxy-N-methylcoclaurine. The Km and Kcat of CyNMCH were estimated and compared with those identified in Eschscholzia californica and Coptis japonica. This newly discovered CyNMCH will provide alternative genetic resources for the synthetic biological production of benzylisoquinoline alkaloids and provides a foundation to help analyze the biosynthetic pathway of BIAs biosynthesis in C. yanhusuo.

Cytochrome P450 Enzymes as Key Drivers of Alkaloid Chemical Diversification in Plants

Plants produce more than 20,000 nitrogen-containing heterocyclic metabolites called alkaloids. These chemicals serve numerous eco-physiological functions in the plants as well as medicines and psychedelic drugs for human for thousands of years, with the anti-cancer agent vinblastine and the painkiller morphine as the best-known examples. Cytochrome P450 monooxygenases (P450s) play a key role in generating the structural variety that underlies this functional diversity of alkaloids. Most alkaloid molecules are heavily oxygenated thanks to P450 enzymes' activities. Moreover, the formation and re-arrangement of alkaloid scaffolds such as ring formation, expansion, and breakage that contribute to their structural diversity and bioactivity are mainly catalyzed by P450s. The fast-expanding genomics and transcriptomics databases of plants have accelerated the investigation of alkaloid metabolism and many players behind the complexity and uniqueness of alkaloid biosynthetic pathways. Here we discuss recent discoveries of P450s involved in the chemical diversification of alkaloids and how these inform our approaches in understanding plant evolution and producing plant-derived drugs.

Enzymatic dimerization in the biosynthetic pathway of microbial natural products

Covering: up to August 2020The dramatic increase in the identification of dimeric natural products generated by microorganisms and plants has played a significant role in drug discovery. The biosynthetic pathways of these products feature inherent dimerization reactions, which are valuable for biosynthetic applications and chemical transformations. The extraordinary mechanisms of the dimerization of secondary metabolites should advance our understanding of the uncommon chemical rules for natural product biosynthesis, which will, in turn, accelerate the discovery of dimeric reactions and molecules in nature and provide promising strategies for the total synthesis of natural products through dimerization. This review focuses on the enzymes involved in the dimerization in the biosynthetic pathway of microbial natural products, with an emphasis on cytochrome P450s, laccases, and intermolecular [4 + 2] cyclases, along with other atypical enzymes. The identification, characterization, and catalytic landscapes of these enzymes are also introduced.

Engineering Saccharomyces cerevisiae to produce plant benzylisoquinoline alkaloids

Benzylisoquinoline alkaloids (BIAs) are a diverse family of plant natural products with extensive pharmacological properties, but the yield of BIAs from plant is limited. The understanding of BIA biosynthetic mechanism in plant and the development of synthetic biology enable the possibility to produce BIAs through microbial fermentation, as an alternative to agriculture-based supply chains. In this review, we discussed the engineering strategies to synthesize BIAs in Saccharomyces cerevisiae (yeast) and improve BIA production level, including heterologous pathway reconstruction, enzyme engineering, expression regulation, host engineering and fermentation engineering. We also highlight recent metabolic engineering advances in the production of BIAs in yeast.

Regio- and stereoselective intermolecular phenol coupling enzymes in secondary metabolite biosynthesis

Covering: 2005 to 2020Phenol coupling is a key reaction in the biosynthesis of important biopolymers such as lignin and melanin and of a plethora of biarylic secondary metabolites. The reaction usually leads to several different regioisomeric products due to the delocalization of a radical in the reaction intermediates. If axial chirality is involved, stereoisomeric products are obtained provided no external factor influences the selectivity. Hence, in non-enzymatic organic synthesis it is notoriously difficult to control the selectivity of the reaction, in particular if the coupling is intermolecular. From biosynthesis, it is known that especially fungi, plants, and bacteria produce biarylic compounds regio- and stereoselectively. Nonetheless, the involved enzymes long evaded discovery. First progress was made in the late 1990s; however, the breakthrough came only with the genomic era and, in particular, in the last few years the number of relevant publications has dramatically increased. The discoveries reviewed in this article reveal a remarkable diversity of enzymes that catalyze oxidative intermolecular phenol coupling, including various classes of laccases, cytochrome P450 enzymes, and heme peroxidases. Particularly in the case of laccases, the catalytic systems are often complex and additional proteins, substrates, or reaction conditions have a strong influence on activity and regio- and atroposelectivity. Although the field of (selective) enzymatic phenol coupling is still in its infancy, the diversity of enzymes identified recently could make it easier to select suitable candidates for biotechnological development and to approach this challenging reaction through biocatalysis.

Comparative Transcriptome Analysis Reveals Candidate Genes Involved in Isoquinoline Alkaloid Biosynthesis in Stephania tetrandra

The roots of Stephania tetrandra are used as a traditional Chinese medicine. Isoquinoline alkaloids are considered to be the most important and effective components in this herb, but little is known about the molecular mechanism underlying their biosynthesis. In this context, this study aimed to reveal candidate genes related to isoquinoline alkaloid biosynthesis in S. tetrandra. Determination of tetrandrine and fangchinoline in the roots and leaves of S. tetrandra by HPLC showed that the roots had much higher contents of the two isoquinoline alkaloids than the leaves. Thus, a comparative transcriptome analysis of the two tissues was performed to uncover candidate genes involved in isoquinoline alkaloid biosynthesis. A total of 71 674 unigenes was obtained and 31 994 of these were assigned putative functions based on BLAST searches against 6 annotation databases. Among the 79 isoquinoline alkaloid-related unigenes, 51 were differentially expressed, with 42 and 9 genes upregulated and downregulated, respectively, when the roots were compared with the leaves. The upregulated differentially expressed genes were consistent with isoquinoline alkaloid accumulation in roots and thus were deemed key candidate genes for isoquinoline alkaloid biosynthesis in the roots. Moreover, the expression profiles of 10 isoquinoline alkaloid-related differentially expressed genes between roots and leaves were validated by quantitative real-time polymerase chain reaction, which indicated that our transcriptome and gene expression profiles were reliable. This study not only provides a valuable genomic resource for S. tetrandra but also proposes candidate genes involved in isoquinoline alkaloid biosynthesis and transcription factors related to the regulation of isoquinoline alkaloid biosynthesis. The results lay a foundation for further studies on isoquinoline alkaloid biosynthesis in this medicinal plant.

Overexpression of GbF3'5'H1 Provides a Potential to Improve the Content of Epicatechin and Gallocatechin

The flavonoids in Ginkgo biloba L. (ginkgo) have important medicinal uses due to their antioxidant, antitumor, and blood circulation-promoting effects. However, the genetic mechanisms underlying flavonoid biosynthesis in ginkgo remain elusive. Flavonoid 3′, 5′-hydroxylase (F3′5′H) is an important enzyme in flavonoid synthesis. We detected a novel differentially expressed GbF3′5′H1 gene homologous to the F3′5′H enzyme involved in the flavonoid synthesis pathway through transcriptome sequencing. In this study, we characterized this gene, performed an expression analysis, and heterologously overexpressed GbF3′5′H1 in Populus. Our results showed that GbF3′5′H1 is abundant in the leaf and highly expressed during April. We also found four metabolites closely related to flavonoid biosynthesis. Importantly, the contents of 4′,5-dihydroxy-7-glucosyloxyflavanone, epicatechin, and gallocatechin were significantly higher in transgenic plants than in nontransgenic plants. Our findings revealed that the GbF3′5′H1 gene functions in the biosynthesis of flavonoid-related metabolites, suggesting that GbF3′5′H1 represents a prime candidate for future studies (e.g., gene-editing) aiming to optimize ginkgo flavonoid production, especially that of flavan-3-ols.

Characterization of O-methyltransferases involved in the biosynthesis of tetrandrine in Stephania tetrandra

Tetrandrine is the most effective small molecule that has been found to inhibit the Ebola virus. It is a typical bisbenzylisoquinoline alkaloid and is the main active ingredient in Stephania tetrandra. Metabolic engineering and synthetic biology are potential methods for efficient and rapid acquisition of tetrandrine. S-adenosyl-L-methionine: (S)-norcoclaurine-6-O-methyltransferase (6OMT) is a rate-limiting step involved in the biosynthesis of tetrandrine. In this study, we identify S-adenosyl-L-methionine: (S)-norcoclaurine-6-O-methyltransferase from S. tetrandra, which catalyzes the conversion of (S)-norcoclaurine to (S)-coclaurine. Four 6OMT-like genes were cloned from S. tetrandra. An in vitro enzyme assay showed that St6OMT1 could catalyze the conversion of (S)-norcoclaurine to produce (S)-coclaurine. St6OMT2 can catalyze the production of very few (S)-coclaurine molecules, accompanied by more by-products with m/z 300, compared to St6OMT1. The newly discovered 6OMTs will provide an optional genetic component for benzylisoquinoline alkaloid (BIA) synthetic biology research. This work will lay the foundation for the analysis of the biosynthetic pathway of tetrandrine in S. tetrandra.

Benzylisoquinoline Alkaloids Biosynthesis in Sacred Lotus

Sacred lotus (Nelumbo nucifera Gaertn.) is an ancient aquatic plant used throughout Asia for its nutritional and medicinal properties. Benzylisoquinoline alkaloids (BIAs), mostly within the aporphine and bisbenzylisoquinoline structural categories, are among the main bioactive constituents in the plant. The alkaloids of sacred lotus exhibit promising anti-cancer, anti-arrhythmic, anti-HIV, and anti-malarial properties. Despite their pharmacological significance, BIA metabolism in this non-model plant has not been extensively investigated. In this review, we examine the diversity of BIAs in sacred lotus, with an emphasis on the distinctive stereochemistry of alkaloids found in this species. Additionally, we discuss our current understanding of the biosynthetic genes and enzymes involved in the formation of 1-benzylisoquinoline, aporphine, and bisbenzylisoquinoline alkaloids in the plant. We conclude that a comprehensive functional characterization of alkaloid biosynthetic enzymes using both in vitro and in vivo methods is required to advance our limited knowledge of BIA metabolism in the sacred lotus.

Pharmacological benefits of neferine - A comprehensive review

This article recapitulates the existing in vitro and in vivo studies focusing on the effects of neferine-an alkaloid derivative of lotus plant, in various disease models and its effects on key signaling molecules. The review also compiles a large number of research studies that demonstrate methods for isolation and extraction, biosynthetic pathway, pharmacological activity and mode of action of neferine and their underlying mechanisms at cellular level. Neferine is a unique bis-benzylisoquinoline alkaloid that possesses a number of therapeutic effects such as anti-cancer, anti-diabetic, anti-aging, anti-microbial, anti-thrombotic, anti-arrhythmic, anti-inflammatory and even anti-HIV. It also enhances the anti-cancer properties of other anti-cancer drugs like cisplatin, adriamycin, taxol, etc. It is also reported to reverse chemo-resistance and enhance sensitivity of the cancer cells towards anti-cancer drugs. The underlying mechanisms for its activities mainly include apoptosis, autophagy and G1 arrest. Neferine protects them against the effect of drugs like cisplatin. The therapeutic properties of neferine is widely diverse, while it shows toxicity to cancer it also shows cyto-protective effects against cardio-vascular diseases, pulmonary disease, and is also effective against Alzheimer's disease and elicits anti-oxidative effect in many cellular systems. This article thus is the first ever attempt to review the therapeutic activities of neferine established in in vitro and in vivo models and to compile all the fragmented data available on the omnipotent activities of neferine.

Mining of the Uncharacterized Cytochrome P450 Genes Involved in Alkaloid Biosynthesis in California Poppy Using a Draft Genome Sequence

Land plants produce specialized low molecular weight metabolites to adapt to various environmental stressors, such as UV radiation, pathogen infection, wounding and animal feeding damage. Due to the large variety of stresses, plants produce various chemicals, particularly plant species-specific alkaloids, through specialized biosynthetic pathways. In this study, using a draft genome sequence and querying known biosynthetic cytochrome P450 (P450) enzyme-encoding genes, we characterized the P450 genes involved in benzylisoquinoline alkaloid (BIA) biosynthesis in California poppy (Eschscholzia californica), as P450s are key enzymes involved in the diversification of specialized metabolism. Our in silico studies showed that all identified enzyme-encoding genes involved in BIA biosynthesis were found in the draft genome sequence of approximately 489 Mb, which covered approximately 97% of the whole genome (502 Mb). Further analyses showed that some P450 families involved in BIA biosynthesis, i.e. the CYP80, CYP82 and CYP719 families, were more enriched in the genome of E. californica than in the genome of Arabidopsis thaliana, a plant that does not produce BIAs. CYP82 family genes were highly abundant, so we measured the expression of CYP82 genes with respect to alkaloid accumulation in different plant tissues and two cell lines whose BIA production differs to estimate the functions of the genes. Further characterization revealed two highly homologous P450s (CYP82P2 and CYP82P3) that exhibited 10-hydroxylase activities with different substrate specificities. Here, we discuss the evolution of the P450 genes and the potential for further genome mining of the genes encoding the enzymes involved in BIA biosynthesis.

Investigation of benzylisoquinoline alkaloid biosynthetic pathway and its transcriptional regulation in lotus

Lotus predominantly accumulates benzylisoquinoline alkaloids (BIAs), but their biosynthesis and regulation remain unclear. Here, we investigated structural and regulatory genes involved in BIA accumulation in lotus. Two clustered CYP80 genes were identified to be responsible for the biosynthesis of bis-BIAs and aporphine-type BIAs, respectively, and their tissue-specific expression causes divergence in alkaloid component between leaf and embryo. In contrast with the common (S)-reticuline precursor for most BIAs, aporphine alkaloids in lotus leaf may result from the (S)-N-methylcoclaurine precursor. Structural diversity of BIA alkaloids in the leaf is attributed to enzymatic modifications, including intramolecular C-C phenol coupling on ring A and methylation and demethylation at certain positions. Additionally, most BIA biosynthetic pathway genes show higher levels of expression in the leaf of high-BIA cultivar compared with low-BIA cultivar, suggesting transcriptional regulation of BIA accumulation in lotus. Five transcription factors, including three MYBs, one ethylene-responsive factor, and one basic helix-loop-helix (bHLH), were identified to be candidate regulators of BIA biosynthesis in lotus. Our study reveals a BIA biosynthetic pathway and its transcriptional regulation in lotus, which will enable a deeper understanding of BIA biosynthesis in plants.

Green Routes for the Production of Enantiopure Benzylisoquinoline Alkaloids

Benzylisoquinoline alkaloids (BIAs) are among the most important plant secondary metabolites, in that they include a number of biologically active substances widely employed as pharmaceuticals. Isolation of BIAs from their natural sources is an expensive and time-consuming procedure as they accumulate in very low levels in plant. Moreover, total synthesis is challenging due to the presence of stereogenic centers. In view of these considerations, green and scalable methods for BIA synthesis using fully enzymatic approaches are getting more and more attention. The aim of this paper is to review fully enzymatic strategies for producing the benzylisoquinoline central precursor, (S)-norcoclaurine and its derivatives. Specifically, we will detail the current status of synthesis of BIAs in microbial hosts as well as using isolated and recombinant enzymes.

Oxidative Cyclization in Natural Product Biosynthesis

Oxidative cyclizations are important transformations that occur widely during natural product biosynthesis. The transformations from acyclic precursors to cyclized products can afford morphed scaffolds, structural rigidity, and biological activities. Some of the most dramatic structural alterations in natural product biosynthesis occur through oxidative cyclization. In this Review, we examine the different strategies used by nature to create new intra(inter)molecular bonds via redox chemistry. This Review will cover both oxidation- and reduction-enabled cyclization mechanisms, with an emphasis on the former. Radical cyclizations catalyzed by P450, nonheme iron, α-KG-dependent oxygenases, and radical SAM enzymes are discussed to illustrate the use of molecular oxygen and S-adenosylmethionine to forge new bonds at unactivated sites via one-electron manifolds. Nonradical cyclizations catalyzed by flavin-dependent monooxygenases and NAD(P)H-dependent reductases are covered to show the use of two-electron manifolds in initiating cyclization reactions. The oxidative installations of epoxides and halogens into acyclic scaffolds to drive subsequent cyclizations are separately discussed as examples of "disappearing" reactive handles. Last, oxidative rearrangement of rings systems, including contractions and expansions, will be covered.

Expansion of chemical space for natural products by uncommon P450 reactions

This review focuses on unusual P450 reactions related to new chemistry, skeleton construction, structure re-shaping, and protein–protein interactions in natural product biosynthesis, which play significant roles in chemical space expansion for natural products.

Digital Gene Expression Analysis Provides Insight into the Transcript Profile of the Genes Involved in Aporphine Alkaloid Biosynthesis in Lotus (Nelumbo nucifera)

The predominant alkaloids in lotus leaves are aporphine alkaloids. These are the most important active components and have many pharmacological properties, but little is known about their biosynthesis. We used digital gene expression (DGE) technology to identify differentially-expressed genes (DEGs) between two lotus cultivars with different alkaloid contents at four leaf development stages. We also predicted potential genes involved in aporphine alkaloid biosynthesis by weighted gene co-expression network analysis (WGCNA). Approximately 335 billion nucleotides were generated; and 94% of which were aligned against the reference genome. Of 22 thousand expressed genes, 19,000 were differentially expressed between the two cultivars at the four stages. Gene Ontology (GO) enrichment analysis revealed that catalytic activity and oxidoreductase activity were enriched significantly in most pairwise comparisons. In Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, dozens of DEGs were assigned to the categories of biosynthesis of secondary metabolites, isoquinoline alkaloid biosynthesis, and flavonoid biosynthesis. The genes encoding norcoclaurine synthase (NCS), norcoclaurine 6-O-methyltransferase (6OMT), coclaurine N-methyltransferase (CNMT), N-methylcoclaurine 3'-hydroxylase (NMCH), and 3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase (4'OMT) in the common pathways of benzylisoquinoline alkaloid biosynthesis and the ones encoding corytuberine synthase (CTS) in aporphine alkaloid biosynthetic pathway, which have been characterized in other plants, were identified in lotus. These genes had positive effects on alkaloid content, albeit with phenotypic lag. The WGCNA of DEGs revealed that one network module was associated with the dynamic change of alkaloid content. Eleven genes encoding proteins with methyltransferase, oxidoreductase and CYP450 activities were identified. These were surmised to be genes involved in aporphine alkaloid biosynthesis. This transcriptomic database provides new directions for future studies on clarifying the aporphine alkaloid pathway.

Bifunctional CYP81AA proteins catalyse identical hydroxylations but alternative regioselective phenol couplings in plant xanthone biosynthesis

Xanthones are natural products present in plants and microorganisms. In plants, their biosynthesis starts with regioselective cyclization of 2,3′,4,6-tetrahydroxybenzophenone to either 1,3,5- or 1,3,7-trihydroxyxanthones, catalysed by cytochrome P450 (CYP) enzymes. Here we isolate and express CYP81AA-coding sequences from Hypericum calycinum and H. perforatum in yeast. Microsomes catalyse two consecutive reactions, that is, 3′-hydroxylation of 2,4,6-trihydroxybenzophenone and C–O phenol coupling of the resulting 2,3′,4,6-tetrahydroxybenzophenone. Relative to the inserted 3′-hydroxyl, the orthologues Hc/HpCYP81AA1 cyclize via the para position to form 1,3,7-trihydroxyxanthone, whereas the paralogue HpCYP81AA2 directs cyclization to the ortho position, yielding the isomeric 1,3,5-trihydroxyxanthone. Homology modelling and reciprocal mutagenesis reveal the impact of S375, L378 and A483 on controlling the regioselectivity of HpCYP81AA2, which is converted into HpCYP81AA1 by sextuple mutation. However, the reciprocal mutations in HpCYP81AA1 barely affect its regiospecificity. Product docking rationalizes the alternative C–O phenol coupling reactions. Our results help understand the machinery of bifunctional CYPs.

Xanthones are pharmacologically and biosynthetically intriguing compounds. Here, the authors identify two cytochrome P450 enzymes, which hydroxylate and cyclize the benzophenone precursor to either 1,3,7- or 1,3,5-trihydroxyxanthones, and pinpoint residues that determine the alternative regioselectivities.

Dirigent Proteins from Cotton (Gossypium sp.) for the Atropselective Synthesis of Gossypol

Gossypol is a defense compound in cotton plants for protection against pests and pathogens. Gossypol biosynthesis involves the oxidative coupling of hemigossypol and results in two atropisomers owing to hindered rotation around the central binaphthyl bond. (+)-Gossypol predominates in vivo, thus suggesting stereochemically controlled biosynthesis. The aim was to identify the factors mediating (+)-gossypol formation in cotton and to investigate their potential for asymmetric biaryl synthesis. A dirigent protein from Gossypium hirsutum (GhDIR4) was found to confer atropselectivity to the coupling of hemigossypol in presence of laccase and O2 as an oxidizing agent. (+)-Gossypol was obtained in greater than 80% enantiomeric excess compared to racemic gossypol in the absence of GhDIR4. The identification of GhDIR4 highlights a broader role for DIRs in plant secondary metabolism and may eventually lead to the development of DIRs as tools for the synthesis of axially chiral binaphthyls.

Synthesis of Morphinan Alkaloids in Saccharomyces cerevisiae

Morphinan alkaloids are the most powerful narcotic analgesics currently used to treat moderate to severe and chronic pain. The feasibility of morphinan synthesis in recombinant Saccharomyces cerevisiae starting from the precursor (R,S)-norlaudanosoline was investigated. Chiral analysis of the reticuline produced by the expression of opium poppy methyltransferases showed strict enantioselectivity for (S)-reticuline starting from (R,S)-norlaudanosoline. In addition, the P. somniferum enzymes salutaridine synthase (PsSAS), salutaridine reductase (PsSAR) and salutaridinol acetyltransferase (PsSAT) were functionally co-expressed in S. cerevisiae and optimization of the pH conditions allowed for productive spontaneous rearrangement of salutaridinol-7-O-acetate and synthesis of thebaine from (R)-reticuline. Finally, we reconstituted a 7-gene pathway for the production of codeine and morphine from (R)-reticuline. Yeast cell feeding assays using (R)-reticuline, salutaridine or codeine as substrates showed that all enzymes were functionally co-expressed in yeast and that activity of salutaridine reductase and codeine-O-demethylase likely limit flux to morphine synthesis. The results of this study describe a significant advance for the synthesis of morphinans in S. cerevisiae and pave the way for their complete synthesis in recombinant microbes.

Comparative functional characterization of a novel benzoate hydroxylase cytochrome P450 of Fusarium oxysporum

FoCYP53A19, a novel cytochrome P450 capable of performing benzoate hydroxylation, was identified and characterized from the ascomycete Fusarium oxysporum f.sp. lycopersici. Comparative functional analysis of FoCYP53A19 with the heterologous and homologous cytochrome P450 reductases (CPR) such as Saccharomyces cerevisiae (ScCPR), Candida albicans (CaCPR) and F. oxysporum (FoCPR) revealed novel catalytic properties. The catalytic efficiency and substrate specificity of FoCYP53A19 were significantly influenced and altered by the source of the reductase employed. The yeast reconstitution system of FoCYP53A19 with ScCPR performed the hydroxylation of benzoic acid (BA) and demethylation of 3-methoxybenzoic acid (3-MBA); but when reconstituted with CaCPR, FoCYP53A19 performed only the essential hydroxylation of fungal benzoate catabolism. Remarkably, FoCYP53A19 with its homologous reductase FoCPR, not only demonstrated the improved conversion rates of BA and 3-MBA, but also exhibited activity toward the hydroxylation of 3-hydroxybenzoic acid. The electron transfer compatibility and the coupling efficiency between the homologous FoCYP-FoCPR system are significant and it favored enhanced monooxygenase activity with broader substrate specificity.

Genome-wide identification and expression analyses of cytochrome P450 genes in mulberry (Morus notabilis)

Cytochrome P450s play critical roles in the biosynthesis of physiologically important compounds in plants. These compounds often act as defense toxins to prevent herbivory. In the present study, a total of 174 P450 genes of mulberry (Morus notabilis C.K.Schn) were identified based on bioinformatics analyses. These mulberry P450 genes were divided into nine clans and 47 families and were found to be expressed in a tissue-preferential manner. These genes were compared to the P450 genes in Arabidopsis thaliana. Families CYP80, CYP92, CYP728, CYP733, CYP736, and CYP749 were found to exist in mulberry, and they may play important roles in the biosynthesis of mulberry secondary metabolites. Analyses of the functional and metabolic pathways of these genes indicated that mulberry P450 genes may participate in the metabolism of lipids, other secondary metabolites, xenobiotics, amino acids, cofactors, vitamins, terpenoids, and polyketides. These results provide a foundation for understanding of the structures and biological functions of mulberry P450 genes.

Benzylisoquinoline alkaloid biosynthesis in opium poppy

Opium poppy (Papaver somniferum) is one of the world's oldest medicinal plants and remains the only commercial source for the narcotic analgesics morphine, codeine and semi-synthetic derivatives such as oxycodone and naltrexone. The plant also produces several other benzylisoquinoline alkaloids with potent pharmacological properties including the vasodilator papaverine, the cough suppressant and potential anticancer drug noscapine and the antimicrobial agent sanguinarine. Opium poppy has served as a model system to investigate the biosynthesis of benzylisoquinoline alkaloids in plants. The application of biochemical and functional genomics has resulted in a recent surge in the discovery of biosynthetic genes involved in the formation of major benzylisoquinoline alkaloids in opium poppy. The availability of extensive biochemical genetic tools and information pertaining to benzylisoquinoline alkaloid metabolism is facilitating the study of a wide range of phenomena including the structural biology of novel catalysts, the genomic organization of biosynthetic genes, the cellular and sub-cellular localization of biosynthetic enzymes and a variety of biotechnological applications. In this review, we highlight recent developments and summarize the frontiers of knowledge regarding the biochemistry, cellular biology and biotechnology of benzylisoquinoline alkaloid biosynthesis in opium poppy.

Research progress relating to the role of cytochrome P450 in the biosynthesis of terpenoids in medicinal plants

Terpenoids are an extensive and diverse group of plant secondary metabolites. To date, they have been applied in many fields including industry, medicine and health. The wide variety of terpenoid compounds cannot arise solely from simple cyclisations of a precursor molecule or from a single-step reaction; their structural diversity depends on the modification of many specific chemical groups, rearrangements of their skeletal structures and on the post-modification reactions. Most of the post-modification enzymes that catalyse these reactions are cytochrome P450 monooxygenases. Therefore, the discovery and identification of plant P450 genes plays a vital role in the exploration of terpenoid biosynthesis pathways. This review summarises recent research progress relating to the function of plant cytochrome P450 enzymes, describes P450 genes that have been cloned from full-length cDNA and identifies the function of P450 enzymes in the terpenoid biosynthesis pathways of several medicinal plants.

CYP82Y1 is N-methylcanadine 1-hydroxylase, a key noscapine biosynthetic enzyme in opium poppy

Noscapine is a phthalideisoquinoline alkaloid investigated for its potent pharmacological properties. Although structurally elucidated more than a century ago, the biosynthesis of noscapine has not been established. Radiotracer studies have shown that noscapine is derived from the protoberberine alkaloid (S)-scoulerine and has been proposed to proceed through (S)-N-methylcanadine. However, pathway intermediates involved in the conversion of N-methylcanadine to noscapine have not been identified. We report the isolation and characterization of the cytochrome P-450 CYP82Y1, which catalyzes the 1-hydroxylation of N-methylcanadine to 1-hydroxy-N-methylcanadine. Comparison of transcript and metabolite profiles of eight opium poppy chemotypes revealed four cytochrome P-450s, three from the CYP82 and one from the CYP719 families, that were tightly correlated with noscapine accumulation. Recombinant CYP82Y1 was the only enzyme that accepted (R,S)-N-methylcanadine as a substrate with strict specificity and high affinity. As expected, CYP82Y1 was abundantly expressed in opium poppy stems where noscapine accumulation is highest among plant organs. Suppression of CYP82Y1 using virus-induced gene silencing caused a significant reduction in the levels of noscapine, narcotoline, and a putative downstream secoberbine intermediate and also resulted in increased accumulation of the upstream pathway intermediates scoulerine, tetrahydrocolum-bamine, canadine, and N-methylcanadine. The combined biochemical and physiological data support the 1-hydroxylation of (S)-N-methylcanadine catalyzed by CYP82Y1 as the first committed step in the formation of noscapine in opium poppy.

Cloning and characterization of canadine synthase involved in noscapine biosynthesis in opium poppy

Noscapine biosynthesis in opium poppy is thought to occur via N-methylcanadine, which would be produced through 9-O-methylation of (S)-scoulerine, methylenedioxy bridge formation on (S)-tetrahydrocolumbamine, and N-methylation of (S)-canadine. Only scoulerine 9-O-methyltransferase has been functionally characterized. We report the isolation and characterization of a cytochrome P450 (CYP719A21) from opium poppy that converts (S)-tetrahydrocolumbamine to (S)-canadine. Recombinant CYP719A21 displayed strict substrate specificity and high affinity (Km=4.63±0.71 μM) for (S)-tetrahydrocolumbamine. Virus-induced gene silencing of CYP719A21 caused a significant increase in (S)-tetrahydrocolumbamine accumulation and a corresponding decrease in the levels of putative downstream intermediates and noscapine in opium poppy plants.

Molecular cloning and characterization of a cytochrome P450 in sanguinarine biosynthesis from Eschscholzia californica cells

Benzophenanthridine alkaloids, such as sanguinarine, are produced from reticuline, a common intermediate in benzylisoquinoline alkaloid biosynthesis, via protopine. Four cytochrome P450s are involved in the biosynthesis of sanguinarine from reticuline; i.e. cheilanthifoline synthase (CYP719A5; EC 1.14.21.2.), stylopine synthase (CYP719A2/A3; EC 1.14.21.1.), N-methylstylopine hydroxylase (MSH) and protopine 6-hydroxylase (P6H; EC 1.14.13.55.). In this study, a cDNA of P6H was isolated from cultured Eschscholzia californica cells, based on an integrated analysis of metabolites and transcript expression profiles of transgenic cells with Coptis japonica scoulerine-9-O-methyltransferase. Using the full-length candidate cDNA for P6H (CYP82N2v2), recombinant protein was produced in Saccharomyces cerevisiae for characterization. The microsomal fraction containing recombinant CYP82N2v2 showed typical reduced CO-difference spectra of P450, and production of dihydrosanguinarine and dihydrochelerythrine from protopine and allocryptopine, respectively. Further characterization of the substrate-specificity of CYP82N2v2 indicated that 6-hydroxylation played a role in the reaction.