Structure of the Cannabis sativa olivetol-producing enzyme reveals cyclization plasticity in type III polyketide synthases

Impact of heterologous expression of Cannabis sativa tetraketide synthase on Phaeodactylum tricornutum metabolic profile

BACKGROUND

Pharmaceutical safety is an increasing global priority, particularly as the demand for therapeutic compounds rises alongside population growth. Phytocannabinoids, a class of bioactive polyketide molecules derived from plants, have garnered significant attention due to their interaction with the human endocannabinoid system, offering potential benefits for managing a range of symptoms and conditions. Traditional extraction from cannabis plants poses regulatory, environmental, and yield-related challenges. Consequently, microbial biosynthesis has emerged as a promising biotechnological alternative to produce cannabinoids in a controlled, scalable, and sustainable manner. Developing diatom-based biofactories represent a crucial step in advancing this biotechnology, enabling the efficient production of high-valued compounds such as cannabinoids.

RESULTS

We engineered the diatom Phaeodactylum tricornutum, a unicellular photosynthetic model organism prized for its naturally high lipid content, to produce olivetolic acid (OA), a key metabolic precursor to most cannabinoids. The genes encoding tetraketide synthase and olivetolic acid cyclase from cannabis were cloned onto episomal vectors and introduced using bacterial conjugation in two separate P. tricornutum transconjugant lines to evaluate enzyme activity and OA production in vivo. Both genes were successfully expressed, and the corresponding enzymes accumulated within the transconjugant lines. However, despite testing the cell extracts individually and in combination, OA accumulation was not detected suggesting potential conversion or utilization of OA by endogenous metabolic pathways within the diatoms. To investigate this further, we analyzed the impact of CsTKS expression on the diatom's metabolome, revealing significant alterations that may indicate metabolic flux redirection or novel pathway interactions.

CONCLUSIONS

Our study demonstrates the successful expression of cannabinoid biosynthetic genes in P. tricornutum but highlights challenges in OA accumulation, likely due to endogenous metabolic interactions. These findings underscore the complexity of metabolic engineering in diatoms and suggest the need for further pathway optimization and metabolic flux analysis to achieve efficient cannabinoid biosynthesis. This research contributes to advancing sustainable biotechnological approaches for cannabinoid production.

Improving CsOAC Activity in Saccharomyces cerevisiae for Directed Production of Olivetolic Acid through Rational Design

Olivetolic acid (OA) is an essential precursor in the cannabinoid biosynthesis. It is produced through a unique interaction between the two proteins, olivetol synthase (CsOLS) and olivetolic acid cyclase (CsOAC). When the OA biosynthesis is transferred to Saccharomyces cerevisiae, olivetol (OL) is produced as a side product, even with a high enhancement of copy number of CsOAC. In order to increase the OA titer while decreasing the OL titer in S. cerevisiae, rational design was applied to CsOAC using in silico approaches such as protein-ligand docking to find potential protein variants. In vivo screening and also testing different approaches for both proteins was applied to identify the best performing variants of CsOAC. Four variants were identified that gave the desired properties. The best CsOAC variant, G82 A/L92Y, resulted in a 1.7-fold increase in OA production and a shift in the ratio between the two products towards OA.

Optimizing hexanoic acid biosynthesis in Saccharomyces cerevisiae for the de novo production of olivetolic acid

Medium chain fatty acids (MCFAs) are valuable platform compounds for the production of biotechnologically relevant chemicals such as biofuels and biochemicals. Two distinct pathways have been implemented in the yeast Saccharomyces cerevisiae for the biosynthetic production of MCFAs: (i) the mutant fatty acid biosynthesis (FAB) pathway in which the fatty acid synthase (FAS) complex is mutated and (ii) a heterologous multispecies-derived reverse β-oxidation (rBOX) pathway. Hexanoic acid has become of great interest as its acyl-CoA ester, hexanoyl-CoA, is required for the biosynthesis of olivetolic acid (OA), a cannabinoid precursor. Due to insufficient endogenous synthesis of hexanoyl-CoA, recombinant microbial systems to date require exogenous supplementation of cultures with hexanoate along with the overexpression of an acyl-CoA ligase to allow cannabinoid biosynthesis. Here, we engineer a recombinant S. cerevisiae strain which was metabolically optimized for the production of hexanoic acid via the FAB and rBOX pathways and we combine both pathways in a single strain to achieve titers of up to 120 mg L-1. Moreover, we demonstrate the biosynthesis of up to 15 mg L-1 OA from glucose using hexanoyl-CoA derived from the rBOX pathway.

Identification and Optimization of more Efficient Olivetolic Acid Synthases

Introduction: Olivetolic acid (OLA) is a key intermediate in cannabidiol (CBD) synthesis, and cannabinoids are important neuroactive drugs. However, the catalytic activity of olivetolic acid synthase (OLS), the key enzyme involved in OLA biosynthesis, remains low and its catalytic mechanism is unclear. Materials and Methods: In this study, we conducted a scrupulous screening of the pivotal rate-limiting enzyme and analyzed its amino acid sites that are critical to enzyme activity as validated by experiments. Results: Through stringent enzyme screening, we pinpointed a highly active OLS sequence, OLS4. Then, we narrowed down three critical amino acid sites (I258, D198, E196) that significantly influence the OLS activity. Conclusions: Our findings laid the groundwork for the efficient biosynthesis of OLA, and thereby facilitate the biosynthesis of CBD.

Understanding metabolic diversification in plants: branchpoints in the evolution of specialized metabolism

Plants are chemical engineers par excellence. Collectively they make a vast array of structurally diverse specialized metabolites. The raw materials for building new pathways (genes encoding biosynthetic enzymes) are commonly recruited directly or indirectly from primary metabolism. Little is known about how new metabolic pathways and networks evolve in plants, or what key nodes contribute to branches that lead to the biosynthesis of diverse chemicals. Here we review the molecular mechanisms underlying the generation of biosynthetic branchpoints. We also consider examples in which new metabolites are formed through the joining of precursor molecules arising from different biosynthetic routes, a scenario that greatly increases both the diversity and complexity of specialized metabolism. Given the emerging importance of metabolic gene clustering in helping to identify new enzymes and pathways, we further cover the significance of biosynthetic gene clusters in relation to metabolic networks and dedicated biosynthetic pathways. In conclusion, an improved understanding of the branchpoints between metabolic pathways will be key in order to be able to predict and illustrate the complex structure of metabolic networks and to better understand the plasticity of plant metabolism. This article is part of the theme issue 'The evolution of plant metabolism'.

Phytochemical Analysis and Antioxidant, Antimicrobial, and Antibiofilm Effects of a New Himalayan Lichen Placidium deosaiense Usman and Khalid Growing in Pakistan

Phytochemical composition and antimicrobial, antibiofilm, and antioxidant effects of a newly described Himalayan lichen Placidium deosaiense Usman and Khalid growing in Pakistan were investigated. HPLC-DAD methods were used for identification of secondary metabolites in acetone and methanol extracts. The total phenolics content was measured using a spectrophotometric method. The study investigated the antioxidant (DPPH-scavenging activity assay and reducing-power assay), antibacterial (minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)), and antibiofilm (inhibition of biofilm formation and reduction in mature biofilm) activities of extracts of the lichen P. deosaiense and isolated parietin. The chemical constituents olivetol, olivetolic acid, haematommic acid, fallacinol, and parietin were identified as major compounds in the tested extracts of the lichen. Parietin was isolated from the acetone extract on a separation column. The methanol extract had higher values of TPC (21.67 mg GAE/g) than the acetone extract. Isolated parietin showed the best antioxidant activity measures, according to the DPPH-scavenging activity assay (IC50 = 51.616 μg/mL) and reducing-power assay. Although the extracts showed the best antibacterial activity (especially against Proteus mirabilis ATCC 12453), parietin demonstrated superior antibiofilm activity (especially against Staphylococcus aureus ATCC 25923). This is the first report on the phytochemical composition of the lichen Placidium deosaiense and the first description of the chemical composition of some of the 45 species of the genus Placidium. This research will pave the way for further exploration of new activities of this lichen and its metabolites, which are important for medicine and pharmacy.

Genome-wide identification of cannabinoid biosynthesis genes in non-drug type Cannabis (Cannabis sativa L.) cultivar

BACKGROUND

Cannabis sativa cultivars can be classified as marijuana or hemp, depending on its amount of the psychoactive cannabinoid Δ9-tetrahydrocannabinolic acid (THCA). Hemp Cheungsam is a non-drug type Cannabis sativa that is characterized by low THCA content. However, the transcripts and expression profile of cannabinoid biosynthesis pathway genes of hemp Cheungsam have not been investigated.

METHODS

RNA-sequencing (RNA-seq) was performed on three different tissue types (flower, leaf, and stem) of hemp Cheungsam to understand their transcriptomes. The expression of cannabinoid biosynthesis pathway genes was further analyzed in each tissue type. Multiple sequence alignment and conserved domain analyses were used to investigate the homologs of cannbinoid biosynthesis genes.

RESULTS

We found that the cannabinoid biosynthesis pathway was mainly expressed in the flowers of hemp Cheungsam, similar to other Cannabis cultivars. However, expression of cannabidiolic acid (CBDA) synthase was much higher than THCA synthase and cannabichromenic acid (CBCA) synthase, suggesting that the transcription profile favors CBDA biosynthesis. Sequence analysis of cannabinoid biosynthesis pathway genes suggested the identity of orthologs in hemp Cheungsam.

CONCLUSIONS

Cannabinoid biosynthesis in hemp Cheungsam mostly occurs in the flowers, compared to other plant organs. While CBDA synthase expression is high, THCA and CBCA synthase expression is considerably low, indicating lesser THCA biosynthesis and thus low THCA content. Sequence analysis of key genes (CBDA, THCA, and CBCA synthases) of the cannabinoid biosynthetic pathway indicates that orthologs are present in hemp Cheungsam.

Effect of Hemp Extraction Procedures on Cannabinoid and Terpenoid Composition

A variety of techniques have been developed to extract hemp phytochemicals for research and consumption. Some of the most common processes in the industry include supercritical CO2 extraction, hydrodistillation, and solvent-based (ethanol) extractions. Each of these processes has the potential to differentially extract various phytochemicals, which would impact their efficacy, tolerability, and safety. However, despite these differences, there has been no direct comparison of the methods and the resulting phytochemical composition. This work aimed to compare cannabinoid and terpene profiles using the three primary commercial procedures, using hemp inflorescence from a CBD/CBG dominant Cannabis sativa L. cultivar. Extracts were then evaluated for their terpene and cannabinoid content using GC-MS and LC-MS/MS, respectively. Hydrodistilled extracts contained the most variety and abundance of terpenes with β-caryophyllene to be the most concentrated terpene (25-42 mg/g). Supercritical CO2 extracts displayed a minimal variety of terpenes, but the most variety and abundance of cannabinoids with CBD ranging from 12.8-20.6 mg/g. Ethanol extracts contained the most acidic cannabinoids with 3.2-4.1 mg/g of CBDA along with minor terpene levels. The resulting extracts demonstrated substantially different chemical profiles and highlight how the process used to extract hemp can play a large role in product composition and potential biological effects.

Advancement of Research Progress on Synthesis Mechanism of Cannabidiol (CBD)

Cannabis sativa L. is a multipurpose crop with high value for food, textiles, and other industries. Its secondary metabolites, including cannabidiol (CBD), have potential for broad application in medicine. With the CBD market expanding, traditional production may not be sufficient. Here we review the potential for the production of CBD using biotechnology. We describe the chemical and biological synthesis of cannabinoids, the associated enzymes, and the application of metabolic engineering, synthetic biology, and heterologous expression to increasing production of CBD.

Engineering cannabinoid production in Saccharomyces cerevisiae

Phytocannabinoids are natural products with highly interesting pharmacological properties mainly produced by plants. The production of cannabinoids in a heterologous host system has gained interest in recent years as a promising alternative to production from plant material. However, the systems reported so far do not achieve industrially relevant titers, highlighting the need for alternative systems. Here, we show the production of the cannabinoids cannabigerolic acid and cannabigerol from glucose and hexanoic acid in a heterologous yeast system using the aromatic prenyltransferase NphB from Streptomyces sp. strain CL190. The production was significantly increased by introducing a fusion protein consisting of ERG20WW and NphB. Furthermore, we improved the production of the precursor olivetolic acid to a titer of 56 mg L-1 . The implementation of the cannabinoid synthase genes enabled the production of Δ9 -tetrahydrocannabinolic acid, cannabidiolic acid as well as cannabichromenic acid, where the heterologous biosynthesis of cannabichromenic acid in a yeast system was demonstrated for the first time. In addition, we found that the product spectrum of the cannabinoid synthases localized to the vacuoles of the yeast cells was highly dependent on extracellular pH, allowing for easy manipulation. Finally, using a fed-batch approach, we showed cannabigerolic acid and olivetolic acid titers of up to 18.2 mg L-1 and 117 mg L-1 , respectively.

Development of an efficient yeast platform for cannabigerolic acid biosynthesis

Cannabinoids are important therapeutical molecules for human ailments, cancer treatment, and SARS-CoV-2. The central cannabinoid, cannabigerolic acid (CBGA), is generated from geranyl pyrophosphate and olivetolic acid by Cannabis sativa prenyltransferase (CsPT4). Despite efforts to engineer microorganisms such as Saccharomyces cerevisiae (S. cerevisiae) for CBGA production, their titers remain suboptimal because of the low conversion of hexanoate into olivetolic acid and the limited activity and stability of the CsPT4. To address the low hexanoate conversion, we eliminated hexanoate consumption by the beta-oxidation pathway and reduced its incorporation into fatty acids. To address CsPT4 limitations, we expanded the endoplasmic reticulum and fused an auxiliary protein to CsPT4. Consequently, the engineered S. cerevisiae chassis showed a marked improvement of 78.64-fold in CBGA production, reaching a titer of 510.32 ± 10.70 mg l-1 from glucose and hexanoate.

Phytocannabinoids biosynthesis during early stages of development of young Cannabis sativa L. seedlings: Integrating biochemical and transcription data

Cannabis sativa (L.) is characterized by great genetic and phenotypic diversity, also expressed in the array of bioactive compounds synthesized. Despite its great potential economic interest, knowledge of the biology and genetics of this crop is incomplete, and still many efforts are needed for a complete understanding of the molecular mechanisms regulating its key traits. To better understand the synthesis of these compounds, we analysed the transcription levels of cannabinoid pathway genes during early phases of plant development, then comparing the transcriptional results with a chemical characterization of the same samples. The work was conducted on both industrial and medicinal C. sativa plants, using samples belonging to three different chemotypes. Genes coding for the cannabinoid synthases, involved in the last step of the cannabinoid biosynthetic pathway, were found to be already expressed in the seed, providing a measure of the importance of this metabolism for the plant. Cannabichromenic acid is known as the first cannabinoid accumulating in the seedlings, shortly after emergence, and it was found that there is a good correspondence between transcript accumulation of the cannabichromenic acid synthase gene and accumulation of the corresponding metabolite.

Biosynthesis of cannabigerol and cannabigerolic acid: the gateways to further cannabinoid production

Cannabinoids are a therapeutically valuable class of secondary metabolites with a vast number of substituents. The native cannabinoid biosynthetic pathway of Cannabis sativa generates cannabigerolic acid (CBGA), the common substrate to multiple cannabinoid synthases. The bioactive decarboxylated analog of this compound, cannabigerol (CBG), represents an alternate gateway into the cannabinoid space as a substrate either to non-canonical cannabinoid synthase homologs or to synthetic chemical reactions. Herein, we describe the identification and repurposing of aromatic prenyltransferase (AtaPT), which when coupled with native enzymes of C. sativa can form an Escherichia coli production system for CBGA in cell lysates and CBG in whole cells. Engineering of AtaPT, guided by structural analysis, was performed to enhance its kinetics toward CBGA production for subsequent use in a proof-of-concept lysate system. For the first time, we show a synthetic biology platform for CBG biosynthesis in E. coli cells by employing AtaPT under an optimized microbial system. Our results have therefore set the foundation for sustainable production of well-researched and rarer cannabinoids in an E. coli chassis. Graphical Abstract.

Parallel evolution of cannabinoid biosynthesis

Modulation of the endocannabinoid system is projected to have therapeutic potential in almost all human diseases. Accordingly, the high demand for novel cannabinoids stimulates the discovery of untapped sources and efficient manufacturing technologies. Here we explored Helichrysum umbraculigerum, an Asteraceae species unrelated to Cannabis sativa that produces Cannabis-type cannabinoids (for example, 4.3% cannabigerolic acid). In contrast to Cannabis, cannabinoids in H. umbraculigerum accumulate in leaves' glandular trichomes rather than in flowers. The integration of de novo whole-genome sequencing data with unambiguous chemical structure annotation, enzymatic assays and pathway reconstitution in Nicotiana benthamiana and in Saccharomyces cerevisiae has uncovered the molecular and chemical features of this plant. Apart from core biosynthetic enzymes, we reveal tailoring ones producing previously unknown cannabinoid metabolites. Orthology analyses demonstrate that cannabinoid synthesis evolved in parallel in H. umbraculigerum and Cannabis. Our discovery provides a currently unexploited source of cannabinoids and tools for engineering in heterologous hosts.

Current status and future prospects in cannabinoid production through in vitro culture and synthetic biology

For centuries, cannabis has been a rich source of fibrous, pharmaceutical, and recreational ingredients. Phytocannabinoids are the most important and well-known class of cannabis-derived secondary metabolites and display a broad range of health-promoting and psychoactive effects. The unique characteristics of phytocannabinoids (e.g., metabolite likeness, multi-target spectrum, and safety profile) have resulted in the development and approval of several cannabis-derived drugs. While most work has focused on the two main cannabinoids produced in the plant, over 150 unique cannabinoids have been identified. To meet the rapidly growing phytocannabinoid demand, particularly many of the minor cannabinoids found in low amounts in planta, biotechnology offers promising alternatives for biosynthesis through in vitro culture and heterologous systems. In recent years, the engineered production of phytocannabinoids has been obtained through synthetic biology both in vitro (cell suspension culture and hairy root culture) and heterologous systems. However, there are still several bottlenecks (e.g., the complexity of the cannabinoid biosynthetic pathway and optimizing the bioprocess), hampering biosynthesis and scaling up the biotechnological process. The current study reviews recent advances related to in vitro culture-mediated cannabinoid production. Additionally, an integrated overview of promising conventional approaches to cannabinoid production is presented. Progress toward cannabinoid production in heterologous systems and possible avenues for avoiding autotoxicity are also reviewed and highlighted. Machine learning is then introduced as a powerful tool to model, and optimize bioprocesses related to cannabinoid production. Finally, regulation and manipulation of the cannabinoid biosynthetic pathway using CRISPR- mediated metabolic engineering is discussed.

Biosynthetic origins of unusual cannabimimetic phytocannabinoids in Cannabis sativa L: A review

Plants of Cannabis sativa L. (Cannabaceae) produce an array of more than 160 isoprenylated resorcinyl polyketides, commonly referred to as phytocannabinoids. These compounds represent molecules of therapeutic importance due to their modulation of the human endocannabinoid system (ECS). While understanding of the biosynthesis of the major phytocannabinoids Δ⁹-tetrahydrocannabinol (Δ⁹-THC) and cannabidiol (CBD) has grown rapidly in recent years, the biosynthetic origin and genetic regulation of many potentially therapeutically relevant minor phytocannabinoids remain unknown, which limits the development of chemotypically elite varieties of C. sativa. This review provides an up-to-date inventory of unusual phytocannabinoids which exhibit cannabimimetic-like activities and proposes putative metabolic origins. Metabolic branch points exploitable for combinatorial biosynthesis and engineering of phytocannabinoids with augmented therapeutic activities are also described, as is the role of phytocannabinoid remodelling to accelerate the therapeutic portfolio expansion in C. sativa.

Dual Engineering of Olivetolic Acid Cyclase and Tetraketide Synthase to Generate Longer Alkyl-Chain Olivetolic Acid Analogs

The therapeutic effects of Δ9-tetrahydrocannabinol (Δ9-THC) can be enhanced by modifications of the pentyl moiety at C-3. The engineering of Cannabis sativa olivetolic acid cyclase and tetraketide synthase with F24I and L190G substitutions, respectively, in the biosynthesis of Δ9-THC serves as a platform for the generation of resorcylic acids up to 6-undecylresorcylic acid. These results provide insights into the development of THC analogs with chemically distinct acyl moieties at C-3.

Expression, purification and structural characterization of resveratrol synthase from Polygonum cuspidatum

Polygonum cuspidatum, an important medicinal plant in China, is a rich source of resveratrol compounds, and its synthesis related resveratrol synthase (RS) gene is highly expressed in stems. The sequence of the resveratrol synthase was amplified with specific primers. Sequence comparison showed that it was highly homologous to the STSs. The RS gene of Polygonum cuspidatum encodes 389 amino acids and has a theoretical molecular weight of 42.4 kDa, which is called PcRS1. To reveal the molecular basis of the synthesized resveratrol activity of PcRS1, we expressed the recombinant protein of full-length PcRS1 in Escherichia coli, and soluble protein products were produced. The collected products were purified by Ni-NTA chelation chromatography and appeared as a single band on SDS-PAGE. In order to obtain higher purity PcRS1, SEC was used to purify the protein and sharp single peak, and DLS detected that the aggregation state of protein molecules was homogeneous and stable. In order to verify the enzyme activity of the high-purity PcRS1, the reaction product was detected at 303 nm. By predicting the structural information of monomer PcRS1 and PcRS1 ligand complexes, we analyzed the ligand binding pocket and protein surface electrostatic potential of the complex, and compared it with the highly homologous STSs protein structures of the iso-ligand. New structural features of protein evolution are proposed. PcRS1 obtained a more complete configuration and the optimal orientation of the active site residues, thus improving its catalytic capacity in resveratrol synthesis.

Anti-Inflammatory Potentials of the n-Hexane Fraction of Alstonia boonei Stem Bark in Lipopolysaccharide-Induced Inflammation in Wistar Rats

Background

Inflammation is a protective response of the host to infections and tissue damage and medicinal plants have been used to regulate inflammatory response. The phytochemical contents of the n-hexane fraction of Alstonia boonei and their anti-inflammatory potentials in lipopolysaccharide-induced inflammation were investigated in rat liver.

Materials and Methods

A quantity of 5 mg/kg lipopolysaccharide (LPS) was used to induce inflammation in twenty-five male Wistar rats, grouped (n = 5) and treated as follows: negative control (10 mL/kg saline), positive control (1 mg/kg ibuprofen); 50, 100 and 20 mg/kg of the n-hexane fraction of Alstonia boonei were administered to test groups. In another experiment, twenty rats (n = 5, without LPS) were administered the same doses of the n-hexane fraction of A. boonei and ibuprofen for seven days. At the end of the experiment, animals were sacrificed, serum was obtained from blood and liver mitochondria isolated in a refrigerated centrifuge. Mitochondrial permeability transition (mPT) pore opening and mitochondrial F₀F₁ ATPase (mATPase) were determined spectrophotometrically. Serum interleukins 1β, 6 (IL-1β, IL-6), tumour necrosis factor alpha (TNF-α), C-reactive protein (CRP) and creatine kinase (CK), gamma glutamyl transferase (GGT), aspartate and alanine aminotransferases (AST and ALT,) of the animals in which inflammation was induced using LPS but treated with graded doses of n-hexane fraction of A. boonei were determined using the ELISA technique. The phytochemical contents of the n-hexane fraction of A. boonei were determined using ultra performance liquid chromatography-tandem mass spectrometer (UHPLC-MS).

Results

Calcium induced mPT in 8 fold and LPS induced mPT 14 fold in the negative control while the n-hexane fraction reversed mPT in the treated groups (50, 100 and 200 mg/kg) to 2, 4, 4 folds, respectively. LPS treatment of the negative group enhanced F₀F₁ mATPase activity, increased CRP, TNF-α, IL-1β, IL-6 levels as well as CK, AST, ALT and GGT activities. These values were significantly reduced by 100 and 200 mg/kg of the n-hexane fraction. UHPLC-MS analysis of the fraction revealed the presence of terpenoids, phenolics and sphingolipids.

Conclusion

These results showed that bioactive phytochemicals present in the n-hexane fraction of A. boonei were not toxic, have an anti-inflammatory effect and could be used for the treatment of inflammatory diseases.

Biosynthesis of Nature-Inspired Unnatural Cannabinoids

Natural products make up a large proportion of medicine available today. Cannabinoids from the plant Cannabis sativa is one unique class of meroterpenoids that have shown a wide range of bioactivities and recently seen significant developments in their status as therapeutic agents for various indications. Their complex chemical structures make it difficult to chemically synthesize them in efficient yields. Synthetic biology has presented a solution to this through metabolic engineering in heterologous hosts. Through genetic manipulation, rare phytocannabinoids that are produced in low yields in the plant can now be synthesized in larger quantities for therapeutic and commercial use. Additionally, an exciting avenue of exploring new chemical spaces is made available as novel derivatized compounds can be produced and investigated for their bioactivities. In this review, we summarized the biosynthetic pathways of phytocannabinoids and synthetic biology efforts in producing them in heterologous hosts. Detailed mechanistic insights are discussed in each part of the pathway in order to explore strategies for creating novel cannabinoids. Lastly, we discussed studies conducted on biological targets such as CB1, CB2 and orphan receptors along with their affinities to these cannabinoid ligands with a view to inform upstream diversification efforts.

The biosynthesis of the cannabinoids

Cannabis has been integral to Eurasian civilization for millennia, but a century of prohibition has limited investigation. With spreading legalization, science is pivoting to study the pharmacopeia of the cannabinoids, and a thorough understanding of their biosynthesis is required to engineer strains with specific cannabinoid profiles. This review surveys the biosynthesis and biochemistry of cannabinoids. The pathways and the enzymes' mechanisms of action are discussed as is the non-enzymatic decarboxylation of the cannabinoic acids. There are still many gaps in our knowledge about the biosynthesis of the cannabinoids, especially for the minor components, and this review highlights the tools and approaches that will be applied to generate an improved understanding and consequent access to these potentially biomedically-relevant materials.

A bio-inspired cell-free system for cannabinoid production from inexpensive inputs

Moving cannabinoid production away from the vagaries of plant extraction and into engineered microbes could provide a consistent, purer, cheaper and environmentally benign source of these important therapeutic molecules, but microbial production faces notable challenges. An alternative to microbes and plants is to remove the complexity of cellular systems by employing enzymatic biosynthesis. Here we design and implement a new cell-free system for cannabinoid production with the following features: (1) only low-cost inputs are needed; (2) only 12 enzymes are employed; (3) the system does not require oxygen and (4) we use a nonnatural enzyme system to reduce ATP requirements that is generally applicable to malonyl-CoA-dependent pathways such as polyketide biosynthesis. The system produces ~0.5 g l-1 cannabigerolic acid (CBGA) or cannabigerovarinic acid (CBGVA) from low-cost inputs, nearly two orders of magnitude higher than yeast-based production. Cell-free systems such as this may provide a new route to reliable cannabinoid production.

Purification and biochemical characterization of Hel a 6, a cross-reactive pectate lyase allergen from Sunflower (Helianthus annuus L.) pollen

Sunflower pollen was reported to contain respiratory allergens responsible for occupational allergy and pollinosis. The present study describes the comprehensive characterization of a major sunflower allergen Hel a 6. Natural Hel a 6 was purified from sunflower pollen by anion exchange and gel filtration chromatography. Hel a 6 reacted with IgE-antibodies from 57% of 39 sunflower-sensitized patient sera suggesting it to be a major allergen. The patients were of Indian origin and suffering from pollinosis and allergic rhinitis. Hel a 6 exhibited allergenic activity by stimulating mediator release from basophils. Monomeric Hel a 6 displayed pectate lyase activity. The effect of various physicochemical parameters such as temperature, pH, and calcium ion on the functional activity of Hel a 6 revealed a stable nature of the protein. Hel a 6 was folded, and its melting curve showed reversible denaturation in which it refolded back to its native conformation from a denatured state. Hel a 6 displayed a high degree of sequence conservation with the pectate lyase allergens from related taxonomic families such as Amb a 1 (67%) and Art v 6 (57%). The IgE-cross reactivity was observed between Hel a 6 and its ragweed and mugwort homologs. The cross-reactivity was further substantiated by the mediator release when Hel a 6-sensitized effector cells were cross-stimulated with Art v 6 and Amb a 1. Several putative B cell epitopes were predicted and mapped on these 3 allergens. Two antigenic regions were found to be commonly shared by these 3 allergens, which could be crucial for cross-reactivity. In conclusion, Hel a 6 serves as a candidate molecule for diagnosis and immunotherapy for weed allergy.