Molecular insights into the enzyme promiscuity of an aromatic prenyltransferase

Catalytic mechanism and engineering of aromatic prenyltransferase: A review

The prenylation of aromatic compounds significantly enhances their metabolic stability and bioactivity. Prenyltransferases, as essential biocatalysts, facilitate the regioselective transfer of prenyl groups from donors to aromatic substrates. This review systematically summarizes recent progress in the rational engineering of prenyltransferases through protein-based strategies, critically evaluates current challenges, and outlines future research priorities. Firstly, we delineate the biosynthetic pathways of prenylated phenolic compounds, emphasizing the pivotal roles of prenyltransferases, and classify these enzymes according to the structural diversity of their aromatic acceptor molecules. Secondly, the current state of prenyltransferase biosynthesis by comparing their heterologous expression levels across diverse microbial hosts is discussed, highlighting key factors influencing catalytic efficiency. Furthermore, we dissect the molecular mechanisms governing prenyltransferase activity and propose innovative engineering approaches integrating artificial intelligence and deep learning to develop high-performance biocatalysts for industrial applications. Finally, we address unresolved challenges in this field, including suboptimal catalytic activity, narrow substrate specificity, and limitations in multi-enzyme cascade systems and immobilization techniques. This review offers strategic insights to guide the engineering and scalable application of prenyltransferases in synthetic biology and pharmaceutical innovation.

Reverse prenylation in plants by non-canonical aromatic prenyltransferases

Reverse-prenylated phenolic compounds are an abundant class of bioactive plant natural products. Hyperixanthone A, an inhibitor of multidrug-resistant Staphylococcus aureus, is a polyprenylated xanthone carrying two forward geminal and one reverse prenyl group. Although prenyltransferases responsible for the forward prenylations were identified, the final reverse prenylation reaction remained elusive. No plant enzyme catalyzing reverse prenylation of an aromatic carbon has been described so far. Here we use metabolic profiling and transcriptomic information from Hypericum perforatum and H. sampsonii to identify homologous enzymes involved in the formation of reverse-prenylated xanthones and characterize their functions using in vitro, in vivo, and in silico approaches. The identified enzymes are non-canonical UbiA-type prenyltransferases, which surprisingly catalyze both forward and reverse prenylations with different regioselectivities. Reconstruction of the enzyme cascade in Saccharomyces cerevisiae and Nicotiana benthamiana confirmed reverse-prenylated hyperixanthone A as the major product. Molecular modeling and docking simulations supported by site-directed mutagenesis suggest two distinct binding modes, which enable forward and reverse prenylations and provide a rationale for the preferred catalysis of the reverse prenyl transfer reaction. The identification of reverse prenylation augments the repertoire of reactions catalyzed by membrane-bound UbiA-type plant aromatic prenyltransferases. The insights also provide a new tool for the biotechnological modification of pharmaceutically valuable natural products.

Prenylation of flavonoids by DMATS1 and their anti-inflammatory activities

BACKGROUND

Prenylated flavonoids are widely distributed in plants, including fruits and vegetables in the Moraceae and Fabaceae families. These chemicals are potential functional food ingredients owing to their attractive biological activities. However, natural prenylated flavonoids are rare, which limits their application.

RESULTS

Here, we reported the prenylation of apigenin and genistein catalyzed by DMATS1, a dimethylallyl-l-tryptophan synthase from Fusarium fujikuroi. High-performance liquid chromatography-tandem mass spectrometry and nuclear magnetic resonance identified their structure as 6-C-prenylapigenin (6-PA) and 6-C-prenylgenistein (6-PG), respectively. Cell-based assay suggested that both 6-PA and 6-PG induced the proliferation of THP-1 cells under low concentrations and were safe in doses less than 50 μmol L-1. 6-PA and 6-PG exhibited significant anti-inflammatory activity in lipopolysaccharide-stimulated THP-1 cells, and inhibited the production of nitric oxide as well as downregulating the transcriptional levels of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-8, and interleukin-1β.

CONCLUSION

The findings suggested that DMATS1 could catalyze the 6-C prenylation of apigenin and genistein, and the generated 6-PA and 6-PG exhibited anti-inflammatory activity, aiding in the recognition of 6-PA and 6-PG as nutraceuticals. © 2025 Society of Chemical Industry.

Heterologous Expression of the Fellutanine Biosynthetic Gene Cluster and Characterization of the Dual Prenylation of cyclo(l-Trp-l-Trp) by a Single DMATS Enzyme

2,5-Diketopiperazines (2,5-DKPs) are recognized for their structural rigidity and diverse bioactivities, making them significant in drug discovery. However, the stereochemical complexity of 2,5-DKPs presents challenges in chemical synthesis, particularly concerning indole derivatives such as indole diketopiperazines (IDKPs). Prenylation and oxidation further diversify these structures, enhancing their bioactivity and membrane affinity. Despite recent advances, the biosynthetic pathways of IDKPs, especially those involving dual prenylation, remain inadequately understood. In this study, the fellutanine biosynthetic gene cluster from Nannizzia fulva was cloned and heterologously expressed in Aspergillus nidulans. A partially oxidized intermediate in the fellutanine biosynthetic pathway was characterized. The dimethylallyl tryptophan synthase (DMATS) enzyme FelB was shown to catalyze consecutive prenylations at two C-2 positions of cyclo(l-Trp-l-Trp) in both in vivo and in vitro assays. Additionally, comparative studies with the known DMATS enzyme OkaC revealed differences in the regioselectivity. Furthermore, the biprenylation mechanism of FelB and OkaC was elucidated through molecular docking and active site analysis.

Biotransformation of Kaempferol to Icaritin in Engineered Saccharomyces cerevisiae

Flavonoids are bioactive natural products known for their pharmaceutical properties and health-promoting applications. Microbial transformation offers a promising and sustainable approach for the biosynthesis of flavonoids. However, challenges such as the lack of well-established synthesis pathways and inefficient heterologous expression of key enzymes limit the flavonoid production such as icaritin. Here, a Saccharomyces cerevisiae strain was engineered to produce icaritin from kaempferol through a metabolic engineering strategy. Enzyme screening strategies identified the functional prenyltransferases, enabling the construction of a bioconversion pathway. The engineered isopentenol and mevalonate pathway boosted the supply of dimethylallyl pyrophosphate, producing 10.4 mg/L 8-prenylkaempferol. Redesigning the N-terminal of prenyltransferase resulted in a 7.5-fold increase in the titer of 8-prenylkaempferol. Cofactor engineering strategies of S-adenosyl-l-methionine recycling resulted in a substantial 139.8% increase in icaritin production. Additionally, the rational design of rate-limiting enzymes significantly improved catalytic performance, enhancing overall icaritin production. Ultimately, engineered S. cerevisiae transformed kaempferol to icaritin successfully through engineered enzymatic modifications with a titer of 14.4 mg/L. This study offers valuable insights into the enzyme design and sustainable natural products production.

Engineering Pichia pastoris for Efficient De Novo Synthesis of 2'-Fucosyllactose

2'-Fucosyllactose (2'-FL), the most abundant in human milk oligosaccharides (HMOs), is a nutrient of great importance. As a safe organism widely used in industries, Pichia pastoris was tested here for 2'-FL production. The de novo biosynthesis pathway of 2'-FL was constructed using genome-editing technology based on CRISPR-Cas9 with an initial titer of 1.01 g/L. Introducing N-terminal SUMO or Ub tag to FucT2 and the transporter CDT2 from Neurospora crassa into P. pastoris was found to improve 2'-FL production. Then, modular metabolic engineering was conducted to improve 2'-FL production, enhancing the GTP supply module, NADPH regeneration module, and precursor supply module. Subsequently, the key enzyme FucT2 was semirationally designed to further increase 2'-FL production. Finally, the 2'-FL production by engineered P. pastoris was scaled up to the 3 L fermenter in fed-batch mode, resulting in a titer of 22.35 g/L that is the highest by P. pastoris. The results prove the effectiveness of the metabolic engineering strategies and demonstrate that P. pastoris could be a potential chassis to produce HMOs.

New insights into exploring new functional enzymes through the enzyme promiscuity

Enzyme promiscuity, defined as the ability of enzymes to catalyze reactions beyond their primary physiological functions, has emerged as a pivotal concept in modern enzyme engineering. This review provides a comprehensive exploration of enzyme promiscuity and its implications for the discovery and development of novel functional enzymes. Through targeted strategies such as (semi-)rational design, directed evolution, and de novo design, enzyme promiscuity has been harnessed to broaden substrate scopes, enhance catalytic efficiencies, and adapt enzymes to diverse reaction conditions. These modifications often involve subtle alterations to the active site, which impact catalytic mechanisms and open new pathways for the synthesis and degradation of complex organic compounds. Striking a balance between maintaining native activity and enhancing promiscuous functions remains a significant challenge in enzyme engineering. Nevertheless, advances in structural biology and computational modeling offer promising strategies to overcome these obstacles. By elucidating the mechanistic basis of enzyme promiscuity, this review aims to deepen our understanding of this phenomenon. It underscores the necessity of further investigating the mechanisms underlying promiscuous enzymatic activity and highlights the importance of leveraging promiscuous enzymes to address industrial application demands and drive the development of next-generation biocatalysts.

Prenylation of Flavanones by an Aromatic Prenyltransferase from Fusarium globosum

Prenylation increases the structural diversity and biological activity of flavonoids. In this study, an aromatic prenyltransferase, FgPT1, was identified from Fusarium globosum. This enzyme was demonstrated to specifically catalyze the prenylation of flavanones, including naringenin, hesperitin, eriodictyol, liquiritigenin, rac-pinocembrin, and dihydrogenistein, and exhibited no activity toward other types of flavonoids, including chalcones, flavonols, isoflavonoids, and flavonols. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and nuclear magnetic resonance (NMR) analysis indicated that the majority of prenylated products were 6-C prenyl flavanones, with the exception of liquiritigenin, which was additionally transformed to 4'-O prenyl liquiritigenin. Enzyme kinetic analysis suggested that FgPT1 exhibited the highest catalytic efficiency towards naringenin, with a kcat/KM value determined as 61.92 s-1 M-1, and the lowest catalytic efficiency towards liquiritigenin, with a kcat/KM of 1.18 s-1 M-1. Biochemical characterization suggested that FgPT1 functioned as a metal-dependent enzyme with optimal activity in the presence of Ba2+ at pH 7.5 and 30 °C. Site-directed mutagenesis resulted in a series of mutants, including A325V with impaired prenylation activity and V116I, V181I, and V194I with enhanced activity. V194I displayed the highest enzymatic activity with a nine-fold increase compared to wild-type FgPT1.

Heterologous Biosynthesis of Prenylflavonoids in Escherichia coli Based on Fungus Screening of Prenyltransferases

Flavonoids are natural products with high biological activity and potential applications. Prenylation increases the lipophilicity of flavonoids, endowing them with specific functions, selectivity, and pharmacological properties. However, traditional methods of plant extraction and chemical synthesis are insufficient to meet the demand for prenylflavonoids. Heterologous biosynthesis of prenylflavonoids in microorganisms provides an alternative approach. Compared with plant prenyltransferases, microbial prenyltransferases showed broad substrate specificity, which is more conducive to the biosynthesis of diverse prenylflavonoids. In this study, we cloned 31 dimethylallyltryptophan synthase prenyltransferases from five fungal species and tested candidate substrates. The products of Ad03 and Ao01 were identified, resulting in two unnatural prenylflavonoids and four natural prenylflavonoids. We constructed the isopentenol utilization pathway in Escherichia coli to develop the efficient dimethylallyl diphosphate synthesis pathway for 6-prenylsilybin (6-PS) synthesis. By optimizing the whole cell catalysis and two-phase reaction system, the 6-PS production titer reached 176 mg/L and the yield of silybin was 88%. Our study provides an efficient method for prenylflavonoids production.

Systematic molecular dissection of key intermediates in xanthones biosynthesis in Cudrania tricuspidata and establishment of a viable heterologous expression system

The major phytochemicals in the roots of Cudrania tricuspidata are prenylated xanthones, exhibiting significant structural diversity and bioactive properties, such as anti-inflammatory, antioxidative, and antitumor effects. The biosynthetic pathways of these compounds have not yet been resolved, limiting their production through synthetic biology. In this study, benzoyl-coenzyme A (CoA) ligase (BZL), benzophenone synthase (BPS), and benzophenone 3'-hydroxylase (B3'H) transcripts involved in the biosynthesis of xanthone were cloned and characterized from C. tricuspidata. The results showed that C. tricuspidata BZL (CtBZL) catalyzed the formation of benzoyl-CoA from benzoate and C. tricuspidata BPS (CtBPS) catalyzed the condensation of benzoyl-CoA and three molecules of malonyl-CoA to form 2,4,6-trihydroxybenzophenone (2,4,6-triHB) via Claisen type cyclization. Then, C. tricuspidata B3'H (CtB3'H) hydroxylated 2,4,6-triHB to produce 2,3',4,6-tetrahydroxybenzophenone (2,3',4,6-tetraHB), which was a key precursor of xanthone derivatives. In addition, the functions of the enzymes were further explored by the heterologous expression of CtBZL, CtBPS, and CtB3'H in Saccharomyces cerevisiae and Nicotiana benthamiana. Also, a preliminary heterologous synthesis system of 2,3',4,6-tetraHB was established. The present study provided the candidate genes and strategies for the heterologous production of xanthones using S. cerevisiae and N. benthamiana as hosts.

Engineering a promiscuous prenyltransferase for selective biosynthesis of an undescribed bioactive cannabinoid analog

Cannabinoids are unique meroterpenoids, with cannabigerolic acid (CBGA) serving as a dedicated precursor. This study introduces a fungal aromatic prenyltransferase AscC into the engineered Escherichia coli to catalyze the transfer of C5-C15 terpenoid linear precursors to olivetolic acid. Four CBGA derivatives (compounds 1-4) with diverse C5, C10, or C15 prenyl chains are isolated and identified, with compound 4 being an undescribed product featuring a C15 prenyl chain at the C-5 position. Compound 4 demonstrates the highest anti-neuroinflammatory and antibacterial activities, with IC50 values of 3.06 µM for TNF-α and 4.31 µM for IL-6, alongside EC50 values ranging from 0.87 to 3.16 µM against three Gram-positive bacteria. An efficient construct is established by incorporating an additional copy of AscC, resulting in a yield of 14.85 ± 0.91 mg/L of compound 4. Two mutants, L180Y and L180F, are engineered to selectively produce compound 4. These findings provide a foundation for enriching the chemical diversity of bioactive cannabinoid analogs with various prenyl moieties through combinatorial biosynthesis.

Characterization and structural analysis of a versatile aromatic prenyltransferase for imidazole-containing diketopiperazines

Prenylation modifications of natural products play essential roles in chemical diversity and bioactivities, but imidazole modification prenyltransferases are not well investigated. Here, we discover a dimethylallyl tryptophan synthase family prenyltransferase, AuraA, that catalyzes the rare dimethylallylation on the imidazole moiety in the biosynthesis of aurantiamine. Biochemical assays validate that AuraA could accept both cyclo-(L-Val-L-His) and cyclo-(L-Val-DH-His) as substrates, while the prenylation modes are completely different, yielding C2-regular and C5-reverse products, respectively. Cryo-electron microscopy analysis of AuraA and its two ternary complex structures reveal two distinct modes for receptor binding, demonstrating a tolerance for altered orientations of highly similar receptors. The mutation experiments further demonstrate the promiscuity of AuraA towards imidazole-C-dimethylallylation. In this work, we also characterize a case of AuraA mutant-catalyzed dimethylallylation of imidazole moiety, offering available structural insights into the utilization and engineering of dimethylallyl tryptophan synthase family prenyltransferases.

Cyclo-farnesyl Diphosphate-Dependent Prenylation in Fungi

A conserved two-gene cassette in fungi was discovered by genome mining, which encodes a UbiA family intramembrane prenyltansferase (VviA) and a haloacid dehalogenase-like hydrolase family terpene cyclase (VviB), respectively. A series of in vivo and in vitro investigations revealed that VviA exclusively uses VviB-synthesized drim-8-ene diphosphate (cyclo-farnesyl diphosphate) as the native prenyl donor to catalyze prenylation on d-mannitol, showcasing a previously unidentified function of UbiA-type prenyltransferases and a new prenylation manner in fungi.

Discovery and Heterologous Expression of Functional 4-O-Dimethylallyl-l-tyrosine Synthases from Lichen-Forming Fungi

Fungal aromatic prenyltransferases are a family of biosynthetic enzymes that catalyze the prenylation of a range of aromatic substrates during the biosynthesis of bioactive indole alkaloids, diketopiperazines, and meroterpenoids. Their broad substrate scope and soluble nature make these enzymes particularly adept for applications in biocatalysis; for example, the enzymatic derivatization of aromatic drugs improves their bioactivity. Here, we investigated four putative aromatic prenyltransferases from lichen-forming fungi, an underexplored group of organisms that produce more than 1,000 unique metabolites. We successfully expressed two enzymes, annotated as dimethylallyltryptophan synthases, from two lichen species in the heterologous host A. oryzae. Based on their in vivo activity, we hypothesize that these enzymes are in fact 4-O-dimethylallyl-l-tyrosine synthases. Our extensive bioinformatic analysis further confirmed that these and related lichen aromatic prenyltransferases are likely not active on indoles but rather on aromatic polyketides and phenylpropanoids, major metabolites in lichens. Overall, our work provides new insights into fungal aromatic prenyltransferases at the family level and enables future efforts aimed at identifying new candidates for biocatalytic transformations of aromatic compounds.

Hosts engineering and in vitro enzymatic synthesis for the discovery of novel natural products and their derivatives

Novel natural products (NPs) and their derivatives are important sources for drug discovery, which have been broadly applied in the fields of agriculture, livestock, and medicine, making the synthesis of NPs and their derivatives necessarily important. In recent years, biosynthesis technology has received increasing attention due to its high efficiency in the synthesis of high value-added novel products and its advantages of green, environmental protection, and controllability. In this review, the technological advances of biosynthesis strategies in the discovery of novel NPs and their derivatives are outlined, with an emphasis on two areas of host engineering and in vitro enzymatic synthesis. In terms of hosts engineering, multiple microorganisms, including Streptomyces, Aspergillus, and Penicillium, have been used as the biosynthetic gene clusters (BGCs) provider and host strain for the expression of BGCs to discover new compounds over the past years. In addition, the use of in vitro enzymatic synthesis strategy to generate novel compounds such as triterpenoid saponins and flavonoids is also hereby described.

Increasing structure diversity of farnesylated chalcones by a fungal aromatic prenyltransferase

Farnesylated chalcones were favored by researchers due to their different biological activities. However, only five naturally occurring farnesylated chalcones were described in the literature until now. Here, the farnesylation of six chalcones by the Aspergillus terreus aromatic prenyltransferase AtaPT was reported. Fourteen monofarnesylated chalcones (1F1-1F5, 2F1-2F3, 3F1, 3F2, 4F1, 4F2, 5F1, 6F1, and 6F2) and a difarnesylated product (2F3) were obtained, enriching the diversity of natural farnesylated chalcones significantly. Ten of them are C-farnesylated products, which complement O-farnesylated chalcones by chemical synthesis. Fourteen products have not been reported prior to this study. Nine of the produced compounds (1F2-1F5, 2F1-2F3, 5F1, and 6F1) exhibited inhibitory effect on α-glucosidase with IC50 values ranging from 24.08 ± 1.44 to 190.0 ± 0.28 μM. Among them, compounds 2F3 with IC50 value at 24.08 ± 1.44 μM and 1F4 with IC50 value at 30.09 ± 0.59 μM showed about 20 times stronger than the positive control acarbose with an IC50 at 536.87 ± 24.25 μM in α-glucosidase inhibitory assays.

Prenylation of aromatic amino acids and plant phenolics by an aromatic prenyltransferase from Rasamsonia emersonii

Dimethylallyl tryptophan synthases (DMATSs) are aromatic prenyltransferases that catalyze the transfer of a prenyl moiety from a donor to an aromatic acceptor during the biosynthesis of microbial secondary metabolites. Due to their broad substrate scope, DMATSs are anticipated as biotechnological tools for producing bioactive prenylated aromatic compounds. Our study explored the substrate scope and product profile of a recombinant RePT, a novel DMATS from the thermophilic fungus Rasamsonia emersonii. Among a variety of aromatic substrates, RePT showed the highest substrate conversion for L-tryptophan and L-tyrosine (> 90%), yielding two mono-prenylated products in both cases. Nine phenolics from diverse phenolic subclasses were notably converted (> 10%), of which the stilbenes oxyresveratrol, piceatannol, pinostilbene, and resveratrol were the best acceptors (37-55% conversion). The position of prenylation was determined using NMR spectroscopy or annotated using MS2 fragmentation patterns, demonstrating that RePT mainly catalyzed mono-O-prenylation on the hydroxylated aromatic substrates. On L-tryptophan, a non-hydroxylated substrate, it preferentially catalyzed C7 prenylation with reverse N1 prenylation as a secondary reaction. Moreover, RePT also possessed substrate-dependent organic solvent tolerance in the presence of 20% (v/v) methanol or DMSO, where a significant conversion (> 90%) was maintained. Our study demonstrates the potential of RePT as a biocatalyst for the production of bioactive prenylated aromatic amino acids, stilbenes, and various phenolic compounds. KEY POINTS: • RePT catalyzes prenylation of diverse aromatic substrates. • RePT enables O-prenylation of phenolics, especially stilbenes. • The novel RePT remains active in 20% methanol or DMSO.

Molecular characterization and structure basis of a malonyltransferase with both substrate promiscuity and catalytic regiospecificity from Cistanche tubulosa

Enzymatic malonylation of natural glycosides provides a promising alternative method for drug-like malonylated glycosides supply. However, the catalytic potential and structural basis of plant malonyltransferase are far from being fully elucidated. This work identified a new malonyltransferase CtMaT1 from Cistanche tubulosa. It displayed unprecedented mono- and/or di-malonylation activity toward diverse glucosides with different aglycons. A "one-pot" system by CtMaT1 and a malonyl-CoA synthetase was established to biosynthesize nine new malonylated glucosides. Structural investigations revealed that CtMaT1 possesses an adequately spacious acyl-acceptor pocket capable of accommodating diverse glucosides. Additionally, it recognizes malonyl-CoA through strong electrotactic and hydrogen interactions. QM/MM calculation revealed the H167-mediated SN2 reaction mechanism of CtMaT1, while dynamic simulations detected the formation of stable hydrogen bonds between the glucose-6-OH group and H167, resulting in its high malonylation regiospecificity. Calculated energy profiles of two isomeric glycosides highlighted lower reaction energy barriers towards glucoside substrates, emphasizing CtMaT1's preference for glucosides. Furthermore, a mutant CtMaT1H36A with notably increased di-malonylation activity was obtained. The underlying molecular mechanism was illuminated through MM/GBSA binding free energy calculation. This study significantly advances the understanding of plant acyltransferases from both functional and protein structural perspectives, while also providing a versatile tool for enzymatic malonylation applications in pharmacology.

Genome Mining Reveals a UbiA-Type Prenyltransferase Access to Farnesylation of Diketopiperazines

UbiA-type prenyltransferases (PTases) are significant enzymes that lead to structurally diverse meroterpenoids. Herein, we report the identification and characterization of an undescribed UbiA-type PTase, FtaB, that is responsible for the farnesylation of indole-containing diketopiperazines (DKPs) through genome mining. Heterologous expression of the fta gene cluster and non-native pathways result in the production of a series of new C2-farnesylated DKPs. This study broadens the reaction scope of UbiA-type PTases and expands the chemical diversity of meroterpenoids.

Selective Late-Stage Functionalization of Tryptophan-Containing Peptides To Facilitate Bioorthogonal Tetrazine Ligation

Site-selective modification of complex peptides and the functionalization of their C-H bonds hold great promise for expanding their use in therapeutics and biomedical research. Herein, we leverage the power of late-stage chemoenzymatic catalysis using an indole prenyltransferase (IPT) enzyme and alkyl diphosphates to specifically modify the indole ring of tryptophan in clinically relevant peptides. Furthermore, the installed handle enables bioorthogonal click chemistry through an inverse electron-demand Diels-Alder (IEDDA) reaction with a biotin-conjugated tetrazine probe.

Structural insights into the diverse prenylating capabilities of DMATS prenyltransferases

Covering: 2009 up to August 2023Prenyltransferases (PTs) are involved in the primary and the secondary metabolism of plants, bacteria, and fungi, and they are key enzymes in the biosynthesis of many clinically relevant natural products (NPs). The continued biochemical and structural characterization of the soluble dimethylallyl tryptophan synthase (DMATS) PTs over the past two decades have revealed the significant promise that these enzymes hold as biocatalysts for the chemoenzymatic synthesis of novel drug leads. This is a comprehensive review of DMATSs describing the structure-function relationships that have shaped the mechanistic underpinnings of these enzymes, as well as the application of this knowledge to the engineering of DMATSs. We summarize the key findings and lessons learned from these studies over the past 14 years (2009-2023). In addition, we identify current gaps in our understanding of these fascinating enzymes.

De novo biosynthesis of the hops bioactive flavonoid xanthohumol in yeast

The flavonoid xanthohumol is an important flavor substance in the brewing industry that has a wide variety of bioactivities. However, its unstable structure results in its low content in beer. Microbial biosynthesis is considered a sustainable and economically viable alternative. Here, we harness the yeast Saccharomyces cerevisiae for the de novo biosynthesis of xanthohumol from glucose by balancing the three parallel biosynthetic pathways, prenyltransferase engineering, enhancing precursor supply, constructing enzyme fusion, and peroxisomal engineering. These strategies improve the production of the key xanthohumol precursor demethylxanthohumol (DMX) by 83-fold and achieve the de novo biosynthesis of xanthohumol in yeast. We also reveal that prenylation is the key limiting step in DMX biosynthesis and develop tailored metabolic regulation strategies to enhance the DMAPP availability and prenylation efficiency. Our work provides feasible approaches for systematically engineering yeast cell factories for the de novo biosynthesis of complex natural products.

A precise swaying map for how promiscuous cellobiose-2-epimerase operate bi-reaction

Promiscuous enzymes play a crucial role in organism survival and new reaction mining. However, comprehensive mapping of the catalytic and regulatory mechanisms hasn't been well studied due to the characteristic complexity. The cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus (CsCE) with complex epimerization and isomerization was chosen to comprehensively investigate the promiscuous mechanisms. Here, the catalytic frame of ring-opening, cis-enediol mediated catalysis and ring-closing was firstly determined. To map the full view of promiscuous CE, the structure of CsCE complex with the isomerized product glucopyranosyl-β1,4-fructose was determined. Combined with computational calculation, the promiscuity was proved a precise cooperation of the double subsites, loop rearrangement, and intermediate swaying. The flexible loop was like a gear, whose structural reshaping regulates the sway of the intermediates between the two subsites of H377-H188 and H377-H247, and thus regulates the catalytic directions. The different protonated states of cis-enediol intermediate catalyzed by H188 were the key point for the catalysis. The promiscuous enzyme tends to utilize all elements at hand to carry out the promiscuous functions.

Yeast-based heterologous production of the Colletochlorin family of fungal secondary metabolites

Transcriptomic studies have revealed that fungal pathogens of plants activate the expression of numerous biosynthetic gene clusters (BGC) exclusively when in presence of a living host plant. The identification and structural elucidation of the corresponding secondary metabolites remain challenging. The aim was to develop a polycistronic system for heterologous expression of fungal BGCs in Saccharomyces cerevisiae. Here we adapted a polycistronic vector for efficient, seamless and cost-effective cloning of biosynthetic genes using in vivo assembly (also called transformation-assisted recombination) directly in Escherichia coli followed by heterologous expression in S. cerevisiae. Two vectors were generated with different auto-inducible yeast promoters and selection markers. The effectiveness of these vectors was validated with fluorescent proteins. As a proof-of-principle, we applied our approach to the Colletochlorin family of molecules. These polyketide secondary metabolites were known from the phytopathogenic fungus Colletotrichum higginsianum but had never been linked to their biosynthetic genes. Considering the requirement for a halogenase, and by applying comparative genomics, we identified a BGC putatively involved in the biosynthesis of Colletochlorins in C. higginsianum. Following the expression of those genes in S. cerevisiae, we could identify the presence of the precursor Orsellinic acid, Colletochlorins and their non-chlorinated counterparts, the Colletorins. In conclusion, the polycistronic vectors described herein were adapted for the host S. cerevisiae and allowed to link the Colletochlorin compound family to their corresponding biosynthetic genes. This system will now enable the production and purification of infection-specific secondary metabolites of fungal phytopathogens. More widely, this system could be applied to any fungal BGC of interest.

Prenylation of dimeric cyclo-L-Trp-L-Trp by the promiscuous cyclo-L-Trp-L-Ala prenyltransferase EchPT1

Prenyltransferases (PTs) from the dimethylallyl tryptophan synthase (DMATS) superfamily are known as efficient biocatalysts and mainly catalyze regioselective Friedel-Crafts alkylation of tryptophan and tryptophan-containing cyclodipeptides (CDPs). They can also use other unnatural aromatic compounds as substrates and play therefore a pivotal role in increasing structural diversity and biological activities of a broad range of natural and unnatural products. In recent years, several prenylated dimeric CDPs have been identified with wide range of bioactivities. In this study, we demonstrate the production of prenylated dimeric CDPs by chemoenzymatic synthesis with a known promiscuous enzyme EchPT1, which uses cyclo-L-Trp-L-Ala as natural substrate for reverse C2-prenylation. High product yields were achieved with EchPT1 for C3-N1' and C3-C3' linked dimers of cyclo-L-Trp-L-Trp. Isolation and structural elucidation confirmed the product structures to be reversely C19/C19'-mono- and diprenylated cyclo-L-Trp-L-Trp dimers. Our study provides an additional example for increasing structural diversity by prenylation of complex substrates with known biosynthetic enzymes. KEY POINTS: • Chemoenzymatic synthesis of prenylated cyclo-L-Trp-L-Trp dimers • Same prenylation pattern and position for cyclodipeptides and their dimers. • Indole prenyltransferases such as EchPT1 can be widely used as biocatalysts.

Ruthenium polypyridine complexes containing prenyl groups as antibacterial agents against Staphylococcus aureus through a membrane-disruption mechanism

Four new ruthenium polypyridyl complexes with prenyl groups, [Ru(bpy)2 (MHIP)](PF6 )2 (Ru(II)-1), [Ru(dtb)2 (MHIP)](PF6 )2 (Ru(II)-2), [Ru(dmb)2 (MHIP)](PF6 )2 (Ru(II)-3), and [Ru(dmob)2 (MHIP)](PF6 )2 (Ru(II)-4) (bpy = 2,2'-bipyridine, dtb = 4,4'-di-tert-butyl-2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine, dmob = 4,4'-dimethoxy-2,2'-bipyridine, and MHIP = 2-(2,6-dimethylhepta-1,5-dien-1-yl)-1H-imidazo[4,f][1,10]phenanthroline), were synthesized and characterized. Their antibacterial activities against Staphylococcus aureus were assessed, and the minimum inhibition concentration (MIC) value of Ru(II)-2 against S. aureus was only 0.5 µg/mL, showing the best antibacterial activity among them. S. aureus could be quickly killed by Ru(II)-2 in 30 min and Ru(II)-2 displayed an obvious inhibitive effect on the formation of a biofilm, which was essential to avoid the development of drug-resistance. Meanwhile, Ru(II)-2 exhibited a stable MIC value against antibiotic-resistant bacteria. The antibacterial mechanism of Ru(II)-2 was probably related to depolarization of the cell membrane, and a change of permeability was associated with the formation of reactive oxygen species, leading to leakage of nucleic acid and bacterial death. Furthermore, Ru(II)-2 hardly showed toxicity to mammalian cells and the Galleria mellonella worm. Finally, murine infection studies also illustrated that Ru(II)-2 was highly effective against S. aureus in vivo.

Non-Native Site-Selective Enzyme Catalysis

The ability to site-selectively modify equivalent functional groups in a molecule has the potential to streamline syntheses and increase product yields by lowering step counts. Enzymes catalyze site-selective transformations throughout primary and secondary metabolism, but leveraging this capability for non-native substrates and reactions requires a detailed understanding of the potential and limitations of enzyme catalysis and how these bounds can be extended by protein engineering. In this review, we discuss representative examples of site-selective enzyme catalysis involving functional group manipulation and C-H bond functionalization. We include illustrative examples of native catalysis, but our focus is on cases involving non-native substrates and reactions often using engineered enzymes. We then discuss the use of these enzymes for chemoenzymatic transformations and target-oriented synthesis and conclude with a survey of tools and techniques that could expand the scope of non-native site-selective enzyme catalysis.

Catalytic site flexibility facilitates the substrate and catalytic promiscuity of Vibrio dual lipase/transferase

Although enzyme catalysis is typified by high specificity, enzymes can catalyze various substrates (substrate promiscuity) and/or different reaction types (catalytic promiscuity) using a single active site. This interesting phenomenon is widely distributed in enzyme catalysis, with both fundamental and applied importance. To date, the mechanistic understanding of enzyme promiscuity is very limited. Herein, we report the structural mechanism underlying the substrate and catalytic promiscuity of Vibrio dual lipase/transferase (VDLT). Crystal structures of the VDLT from Vibrio alginolyticus (ValDLT) and its fatty acid complexes were solved, revealing prominent structural flexibility. In particular, the "Ser-His-Asp" catalytic triad machinery of ValDLT contains an intrinsically flexible oxyanion hole. Analysis of ligand-bound structures and mutagenesis showed that the flexible oxyanion hole and other binding residues can undergo distinct conformational changes to facilitate substrate and catalytic promiscuity. Our study reveals a previously unknown flexible form of the famous catalytic triad machinery and proposes a "catalytic site tuning" mechanism to expand the mechanistic paradigm of enzyme promiscuity.

CRISPR-Cas9 Gene Editing and Secondary Metabolite Screening Confirm Fusarium graminearum C16 Biosynthetic Gene Cluster Products as Decalin-Containing Diterpenoid Pyrones

Fusarium graminearum is a causal organism of Fusarium head blight in cereals and maize. Although a few secondary metabolites produced by F. graminearum are considered disease virulence factors, many molecular products of biosynthetic gene clusters expressed by F. graminearum during infection and their associated role in the disease are unknown. In particular, the predicted meroterpenoid products of the biosynthetic gene cluster historically designated as "C16" are likely associated with pathogenicity. Presented here are the results of CRISPR-Cas9 gene-editing experiments disrupting the polyketide synthase and terpene synthase genes associated with the C16 biosynthetic gene cluster in F. graminearum. Culture medium screening experiments using transformant strains were profiled by UHPLC-HRMS and targeted MS² experiments to confirm the associated secondary metabolite products of the C16 biosynthetic gene cluster as the decalin-containing diterpenoid pyrones, FDDP-D and FDDP-E. Both decalin-containing diterpenoid pyrones were confirmed to be produced in wheat heads challenged with F. graminearum in growth chamber trials. The extent to which the F. graminearum C16 biosynthetic gene cluster is dispersed within the genus Fusarium is discussed along with a proposed role of the FDDPs as pathogen virulence factors.

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.

Phytochemistry and pharmacology of natural prenylated flavonoids

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

Geranylation of Chalcones by a Fungal Aromatic Prenyltransferase

Geranylated chalcones mainly exist in plants, and many of them have attracted attention because of their diverse pharmacological and biological activities. Herein, we report geranylation of eight chalcones by the Aspergillus terreus aromatic prenyltransferase AtaPT. Ten new mono-geranylated enzyme products (1G-5G, 6G1, 6G2, 7G, 8G1, and 8G2) were obtained. Most of the products are C-geranylated products with prenyl moieties at ring B. In comparison, plant aromatic prenyltransferases usually catalyze the geranylation at ring A. Therefore, AtaPT can be used complementarily for chalcone geranylation to increase the structural diversity of small molecules. In addition, seven compounds (1G, 3G, 4G, 6G1, 7G, 8G1, and 8G2) exhibited a potential inhibitory effect on α-glucosidase with the IC₅₀ values ranging from 45.59 ± 3.48 to 82.85 ± 2.15 μg/mL. Among them, compound 7G (45.59 ± 3.48 μg/mL) was the most potential α-glucosidase inhibitor, which is about seven times stronger than the positive control acarbose (IC₅₀ = 346.63 ± 15.65 μg/mL).

Prenylation: A Critical Step for Biomanufacturing of Prenylated Aromatic Natural Products

Prenylated aromatic natural products (PANPs) have received much attention due to their biomedical benefits for human health. The prenylation of aromatic natural products (ANPs), which is mainly catalyzed by aromatic prenyltransferases (aPTs), contributes significantly to their structural and functional diversity by providing higher lipophilicity and enhanced bioactivity. aPTs are widely distributed in bacteria, fungi, animals, and plants and play a key role in the regiospecific prenylation of ANPs. Recent studies have greatly advanced our understanding of the characteristics and application of aPTs. In this review, we comment on research progress regarding sources, evolutionary relationships, structural features, reaction mechanism, engineering modification, and application of aPTs. Particular emphasis is also placed on recent advances, challenges, and prospects about applications of aPTs in microbial cell factories for producing PANPs. Generally, this review could provide guidance for using aPTs as robust biocatalytic tools to produce various PANPs with high efficiency.

Enhancing lactose recognition of a key enzyme in 2'-fucosyllactose synthesis: α-1,2-fucosyltransferase

BACKGROUND

2'-Fucosyllactose, a representative oligosaccharide in human milk, is an emerging and promising food and pharmaceutical ingredient due to its powerful health benefits, such as participating in immune regulation, regulation of intestinal flora, etc. To enable economically viable production of 2'-fucosyllactose, different biosynthesis strategies using precursors and pathway enzymes have been developed. The α-1,2-fucosyltransferases are an essential part involved in these strategies, but their strict substrate selectivity and unsatisfactory substrate tolerance are one of the key roadblocks limiting biosynthesis.

RESULTS

To tackle this issue, a semi-rational manipulation combining computer-aided designing and screening with biochemical experiments were adopted. The mutant had a 100-fold increase in catalytic efficiency compared to the wild-type. The highest 2'-fucosyllactose yield was up to 0.65 mol mol^-1 lactose with a productivity of 2.56 g mL^-1  h^-1 performed by enzymatic catalysis in vitro. Further analysis revealed that the interactions between the mutant and substrates were reduced. The crucial contributions of wild-type and mutant to substrate recognition ability were closely related to their distinct phylotypes in terms of amino acid preference.

CONCLUSION

It is envisioned that the engineered α-1,2-fucosyltransferase could be harnessed to relieve constraints imposed on the bioproduction of 2'-fucosyllactose and lay a theoretical foundation for elucidating the substrate recognition mechanisms of fucosyltransferases. © 2022 Society of Chemical Industry.

Data Science-Driven Analysis of Substrate-Permissive Diketopiperazine Reverse Prenyltransferase NotF: Applications in Protein Engineering and Cascade Biocatalytic Synthesis of (-)-Eurotiumin A

Prenyltransfer is an early-stage carbon-hydrogen bond (C-H) functionalization prevalent in the biosynthesis of a diverse array of biologically active bacterial, fungal, plant, and metazoan diketopiperazine (DKP) alkaloids. Toward the development of a unified strategy for biocatalytic construction of prenylated DKP indole alkaloids, we sought to identify and characterize a substrate-permissive C2 reverse prenyltransferase (PT). As the first tailoring event within the biosynthesis of cytotoxic notoamide metabolites, PT NotF catalyzes C2 reverse prenyltransfer of brevianamide F. Solving a crystal structure of NotF (in complex with native substrate and prenyl donor mimic dimethylallyl S-thiolodiphosphate (DMSPP)) revealed a large, solvent-exposed active site, intimating NotF may possess a significantly broad substrate scope. To assess the substrate selectivity of NotF, we synthesized a panel of 30 sterically and electronically differentiated tryptophanyl DKPs, the majority of which were selectively prenylated by NotF in synthetically useful conversions (2 to >99%). Quantitative representation of this substrate library and development of a descriptive statistical model provided insight into the molecular origins of NotF's substrate promiscuity. This approach enabled the identification of key substrate descriptors (electrophilicity, size, and flexibility) that govern the rate of NotF-catalyzed prenyltransfer, and the development of an "induced fit docking (IFD)-guided" engineering strategy for improved turnover of our largest substrates. We further demonstrated the utility of NotF in tandem with oxidative cyclization using flavin monooxygenase, BvnB. This one-pot, in vitro biocatalytic cascade enabled the first chemoenzymatic synthesis of the marine fungal natural product, (-)-eurotiumin A, in three steps and 60% overall yield.

Challenges in the Heterologous Production of Furanocoumarins in Escherichia coli

Coumarins and furanocoumarins are plant secondary metabolites with known biological activities. As they are present in low amounts in plants, their heterologous production emerged as a more sustainable and efficient approach to plant extraction. Although coumarins biosynthesis has been positively established, furanocoumarin biosynthesis has been far more challenging. This study aims to evaluate if Escherichia coli could be a suitable host for furanocoumarin biosynthesis. The biosynthetic pathway for coumarins biosynthesis in E. coli was effectively constructed, leading to the production of umbelliferone, esculetin and scopoletin (128.7, 17.6, and 15.7 µM, respectively, from tyrosine). However, it was not possible to complete the pathway with the enzymes that ultimately lead to furanocoumarins production. Prenyltransferase, psoralen synthase, and marmesin synthase did not show any activity when expressed in E. coli. Several strategies were tested to improve the enzymes solubility and activity with no success, including removing potential N-terminal transit peptides and expression of cytochrome P450 reductases, chaperones and/or enzymes to increase dimethylallylpyrophosphate availability. Considering the results herein obtained, E. coli does not seem to be an appropriate host to express these enzymes. However, new alternative microbial enzymes may be a suitable option for reconstituting the furanocoumarins pathway in E. coli. Nevertheless, until further microbial enzymes are identified, Saccharomyces cerevisiae may be considered a preferred host as it has already been proven to successfully express some of these plant enzymes.

The Biosynthesis Related Enzyme, Structure Diversity and Bioactivity Abundance of Indole-Diterpenes: A Review

Indole diterpenes are a large class of secondary metabolites produced by fungi, possessing a cyclic diterpenoid backbone and an indole moiety. Novel structures and important biological activity have made indole diterpenes one of the focuses of synthetic chemists. Although the discovery, identification, structural diversity, biological activity and especially structure-activity relationship of indole diterpenes have been reported in some papers in recent years, they are absent of a systematic and comprehensive analysis, and there is no elucidation of enzymes related to this kind of natural product. Therefore, it is necessary to summarize the relevant reports to provide new perspectives for the following research. In this review, for the first time, the function of related synthases and the structure-activity relationship of indole diterpenes are expounded, and the recent research advances of them are emphasized.

Structural diversification of bioactive bibenzyls through modular co-culture leading to the discovery of a novel neuroprotective agent

Bibenzyls, a kind of important plant polyphenols, have attracted growing attention for their broad and remarkable pharmacological activities. However, due to the low abundance in nature, uncontrollable and environmentally unfriendly chemical synthesis processes, these compounds are not readily accessible. Herein, one high-yield bibenzyl backbone-producing Escherichia coli strain was constructed by using a highly active and substrate-promiscuous bibenzyl synthase identified from Dendrobium officinale in combination with starter and extender biosynthetic enzymes. Three types of efficiently post-modifying modular strains were engineered by employing methyltransferases, prenyltransferase, and glycosyltransferase with high activity and substrate tolerance together with their corresponding donor biosynthetic modules. Structurally different bibenzyl derivatives were tandemly and/or divergently synthesized by co-culture engineering in various combination modes. Especially, a prenylated bibenzyl derivative (12) was found to be an antioxidant that exhibited potent neuroprotective activity in the cellular and rat models of ischemia stroke. RNA-seq, quantitative RT-PCR, and Western-blot analysis demonstrated that 12 could up-regulate the expression level of an apoptosis-inducing factor, mitochondria associated 3 (Aifm3), suggesting that Aifm3 might be a new target in ischemic stroke therapy. This study provides a flexible plug-and-play strategy for the easy-to-implement synthesis of structurally diverse bibenzyls through a modular co-culture engineering pipeline for drug discovery.

Structural Basis of Substrate Promiscuity and Catalysis by the Reverse Prenyltransferase N-Dimethylallyl-l-tryptophan Synthase from Fusarium fujikuroi

The regiospecific prenylation of an aromatic amino acid catalyzed by a dimethylallyl-l-tryptophan synthase (DMATS) is a key step in the biosynthesis of many fungal and bacterial natural products. DMATS enzymes share a common "ABBA" fold with divergent active site contours that direct alternative C-C, C-N, and C-O bond-forming trajectories. DMATS1 from Fusarium fujikuroi catalyzes the reverse N-prenylation of l-Trp by generating an allylic carbocation from dimethylallyl diphosphate (DMAPP) that then alkylates the indole nitrogen of l-Trp. DMATS1 stands out among the greater DMATS family because it exhibits unusually broad substrate specificity: it can utilize geranyl diphosphate (GPP) or l-Tyr as an alternative prenyl donor or acceptor, respectively; it can catalyze both forward and reverse prenylation, i.e., at C1 or C3 of DMAPP; and it can catalyze C-N and C-O bond-forming reactions. Here, we report the crystal structures of DMATS1 and its complexes with l-Trp or l-Tyr and unreactive thiolodiphosphate analogues of the prenyl donors DMAPP and GPP. Structures of ternary complexes mimic Michaelis complexes with actual substrates and illuminate active site features that govern prenylation regiochemistry. Comparison with CymD, a bacterial enzyme that catalyzes the reverse N-prenylation of l-Trp with DMAPP, indicates that bacterial and fungal DMATS enzymes share a conserved reaction mechanism. However, the narrower active site contour of CymD enforces narrower substrate specificity. Structure-function relationships established for DMATS enzymes will ultimately inform protein engineering experiments that will broaden the utility of these enzymes as useful tools for synthetic biology.

Biocatalytic Friedel-Crafts Reactions

Friedel-Crafts alkylation and acylation reactions are important methodologies in synthetic and industrial chemistry for the construction of aryl-alkyl and aryl-acyl linkages that are ubiquitous in bioactive molecules. Nature also exploits these reactions in many biosynthetic processes. Much work has been done to expand the synthetic application of these enzymes to unnatural substrates through directed evolution. The promise of such biocatalysts is their potential to supersede inefficient and toxic chemical approaches to these reactions, with mild operating conditions - the hallmark of enzymes. Complementary work has created many bio-hybrid Friedel-Crafts catalysts consisting of chemical catalysts anchored into biomolecular scaffolds, which display many of the same desirable characteristics. In this Review, we summarise these efforts, focussing on both mechanistic aspects and synthetic considerations, concluding with an overview of the frontiers of this field and routes towards more efficient and benign Friedel-Crafts reactions for the future of humankind.

Molecular mechanism of acceptor selection in cyclodextrin glycosyltransferases catalyzed ginsenoside transglycosylation

Understanding the mechanisms of enzyme specificity is increasingly important from a fundamental viewpoint and for practical applications. Transglycosylation has attracted many attentions due to its importance in improving the functional properties of acceptor substrates both in vivo and in vitro. Cyclodextrin glucanotransferase (CGTase) is one of the key enzymes in transglycosylation, it has a broad substrate spectrum and utilizes sugar as the donor. However, little is known about the acceptor selectivity of CGTase, which greatly hampers efforts toward the rational design of desirable transglycosylated derivatives. In this study, we found that the CGTase from Bacillus circulans, BcCGTase, was able to form glycosylated products with diverse ginsenosides. In particular, it not only carries out diverse mono-, di-, and even higher-order glycosylations via the transfer of glucose moieties to the COGlc positions, but also can glycosylate the C3-OH position of ginsenosides. In contrast, another CGTase from Bacillus licheniformis (BlCGTase) showed relatively specific acceptor preference with only several ginsenosides. Structural comparison between BcCGTase and BlCGTase revealed that the Arg74/K81 position within the acceptor-binding sites of BcCGTase/BlCGTase was responsible for the differences in catalytic specificity for ginsenoside F1. Further mutagenesis confirmed their roles in the acceptor selection. In conclusion, our study not only demonstrates the acceptor selectivity of CGTases, but also provides insight into the catalytic mechanism of CGTases, which will potentially increase the utility of CGTase for biosynthesis of new, rationally designed transglycosylated derivatives.

Biosynthesis of pyrroloindoline-containing natural products

Covering: up to 2022Pyrroloindoline is a privileged tricyclic indoline motif widely present in many biologically active and medicinally valuable natural products. Thus, understanding the biosynthesis of this molecule is critical for developing convenient synthetic routes, which is highly challenging for its chemical synthesis due to the presence of rich chiral centers in this molecule, especially the fully substituted chiral carbon center at the C3-position of its rigid tricyclic structure. In recent years, progress has been made in elucidating the biosynthetic pathways and enzymatic mechanisms of pyrroloindoline-containing natural products (PiNPs). This article reviews the main advances in the past few decades based on the different substitutions on the C3 position of PiNPs, especially the various key enzymatic mechanisms involved in the biosynthesis of different types of PiNPs.

Recent Advances in the Synthesis of Marine-Derived Alkaloids via Enzymatic Reactions

Alkaloids are a large and structurally diverse group of marine-derived natural products. Most marine-derived alkaloids are biologically active and show promising applications in modern (agro)chemical, pharmaceutical, and fine chemical industries. Different approaches have been established to access these marine-derived alkaloids. Among these employed methods, biotechnological approaches, namely, (chemo)enzymatic synthesis, have significant potential for playing a central role in alkaloid production on an industrial scale. In this review, we discuss research progress on marine-derived alkaloid synthesis via enzymatic reactions and note the advantages and disadvantages of their applications for industrial production, as well as green chemistry for marine natural product research.

Xanthone Biosynthetic Pathway in Plants: A Review

Xanthones are secondary metabolites rich in structural diversity and possess a broad array of pharmacological properties, such as antitumor, antidiabetic, and anti-microbes. These aromatic compounds are found in higher plants, such as Clusiaceae, Hypericaceae, and Gentianaceae, yet their biosynthetic pathways have not been comprehensively updated especially within the last decade (up to 2021). In this review, plant xanthone biosynthesis is detailed to illuminate their intricacies and differences between species. The pathway initially involves the shikimate pathway, either through L-phenylalanine-dependent or -independent pathway, that later forms an intermediate benzophenone, 2,3',4,6-tetrahydoxybenzophenone. This is followed by a regioselective intramolecular mediated oxidative coupling to form xanthone ring compounds, 1,3,5-trihydroxyxanthone (1,3,5-THX) or 1,3,7-THX, the core precursors for xanthones in most plants. Recent evidence has shed some lights onto the enzymes and reactions involved in this xanthone pathway. In particular, several biosynthetic enzymes have been characterized at both biochemical and molecular levels from various organisms including Hypericum spp., Centaurium erythraea and Garcinia mangostana. Proposed pathways for a plethora of other downstream xanthone derivatives including swertianolin and gambogic acid (derived from 1,3,5-THX) as well as gentisin, hyperixanthone A, α-mangostin, and mangiferin (derived from 1,3,7-THX) have also been thoroughly covered. This review reports one of the most complete xanthone pathways in plants. In the future, the information collected here will be a valuable resource for a more directed molecular works in xanthone-producing plants as well as in synthetic biology application.

Increasing Structural Diversity of Prenylated Chalcones by Two Fungal Prenyltransferases

Prenylated chalcones are found mainly in plants and exhibit diverse biological and pharmacological activities. Some of these compounds are components of food and dietary supplements with significant health benefits. In plants, they are derived from chalcones by prenylation with membrane-bound prenyltransferases. In this study, we demonstrate prenylations of 10 chalcones by two fungal prenyltransferases (AtaPT/AnaPT) in the presence of dimethylallyl diphosphate. Eleven mono- (1a-10a and 9b) and four diprenylated products (8b, 9c, 10b, and 10c) were obtained. Among them, 12 have new structures (1a, 2a, 4a-6a, 8a, 8b, 9b, 9c, 10a, 10b, and 10c). Most of the obtained prenylated chalcones are products of AnaPT and carry prenyl moieties at ring B. Our study provides an excellent example for increasing structural diversity of plant metabolites with microbial enzymes.