Chemoproteomics reveals the epoxidase enzyme for the biosynthesis of camptothecin in Ophiorrhiza pumila

The downstream biosynthetic route of camptothecin has remained unclear for more than half a century. Here, we discovered a P450 enzyme involved in camptothecin biosynthesis from plant by chemoproteomics, which lays the foundation for synthesis of camptothecin and highlights the effectiveness of chemoproteomic profiling for discovering unknown enzymes.

Progress in Identification of UDP-Glycosyltransferases for Ginsenoside Biosynthesis

Ginsenosides, the primary pharmacologically active constituents of the Panax genus, have demonstrated a variety of medicinal properties, including anticardiovascular disease, cytotoxic, antiaging, and antidiabetes effects. However, the low concentration of ginsenosides in plants and the challenges associated with their extraction impede the advancement and application of ginsenosides. Heterologous biosynthesis represents a promising strategy for the targeted production of these natural active compounds. As representative triterpenoids, the biosynthetic pathway of the aglycone skeletons of ginsenosides has been successfully decoded. While the sugar moiety is vital for the structural diversity and pharmacological activity of ginsenosides, the mining of uridine diphosphate-dependent glycosyltransferases (UGTs) involved in ginsenoside biosynthesis has attracted a lot of attention and made great progress in recent years. In this paper, we summarize the identification and functional study of UGTs responsible for ginsenoside synthesis in both plants, such as Panax ginseng and Gynostemma pentaphyllum, and microorganisms including Bacillus subtilis and Saccharomyces cerevisiae. The UGT-related microbial cell factories for large-scale ginsenoside production are also mentioned. Additionally, we delve into strategies for UGT mining, particularly potential rapid screening or identification methods, providing insights and prospects. This review provides insights into the study of other unknown glycosyltransferases as candidate genetic elements for the heterologous biosynthesis of rare ginsenosides.

UDP-glycosyltransferase gene SlUGT73C1 from Solanum lycopersicum regulates salt and drought tolerance in Arabidopsis thaliana L

Among abiotic stresses, plants are the most vulnerable to salt and drought stresses. These stresses affect plant growth and development. Glycosyltransferases are involved in the responses of plants to abiotic stresses. In this study, a UDP-glycosyltransferase gene (SlUGT73C1) from Solanum lycopersicum was isolated and identified, which exhibited induction under salt or drought stress. The full length of SlUGT73C1 was 1485 bp, encoding 494 amino acids. Stress-related cis-acting elements were present in the promoter sequence of SlUGT73C1, such as ARE, LTR, and GC motifs. Compared with the wild-type plants, Arabidopsis thaliana overexpressing SlUGT73C1 exhibited increased seed germination rate and SOD and POD activities, decreased MDA content, and increased expression levels of osmotic stress regulators genes, rate-limiting enzymes genes in the proline synthesis pathway, Na+/K+ reverse transporter genes, and rate-limiting genes in the ABA biosynthesis pathway under salt or drought stress. These results indicated that SlUGT73C1 plays an important role in regulating salt and drought tolerance in plants.

UDP-Glycosyltransferases in Edible Fungi: Function, Structure, and Catalytic Mechanism

UDP-glycosyltransferases (UGTs) are the most studied glycosyltransferases, and belong to large GT1 family performing the key roles in antibiotic synthesis, the development of bacterial glycosyltransferase inhibitors, and in animal inflammation. They transfer the glycosyl groups from nucleotide UDP-sugars (UDP-glucose, UDP-galactose, UDP-xylose, and UDP-rhamnose) to the acceptors including saccharides, proteins, lipids, and secondary metabolites. The present review summarized the recent of UDP-glycosyltransferases, including their structures, functions, and catalytic mechanism, especially in edible fungi. The future perspectives and new challenges were also summarized to understand of their structure–function relationships in the future. The outputs in this field could provide a reference to recognize function, structure, and catalytic mechanism of UDP-glycosyltransferases for understanding the biosynthesis pathways of secondary metabolites, such as hydrocarbons, monoterpenes, sesquiterpene, and polysaccharides in edible fungi.

Screening UDP-Glycosyltransferases for Effectively Transforming Stevia Glycosides: Enzymatic Synthesis of Glucosylated Derivatives of Rubusoside

Five plant-derived uridine diphosphate glycosyltransferases (UGTs) that catalyzed the glucosylation of stevia glycosides (SGs) were uncovered as the result of sequence mining considering the catalytic residues and conserved motifs of the known UGTs. Thereinto, LbUGT from Lycium barbarum with high activity toward rubusoside has been enzymatically characterized. The recombinant LbUGT was demonstrated to catalyze the β-1,6-glucosylation at C19 of rubusoside, producing a monoglucosyl derivative 13-[(O-β-d-glucopyranosyl) oxy] ent-kaur-16-en-19-oic acid-[(6-O-β-d-glucopyranosyl-β-d-glucopyranosyl) ester], which was then submitted to a β-1,2-glucosylation by LbUGT, resulting in a diglucosyl derivative 13-[(O-β-d-glucopyranosyl) oxy] ent-kaur-16-en-19-oic acid-[(2-O-β-d-glucopyranosyl-6-O-β-d-glucopyranosyl-β-d-glucopyranosyl) ester]. The di-glycosylated product of rubusoside showed an obvious increase in sweetness intensity (134 times sweeter than 5% sucrose) and almost eliminated the unpleasant bitter taste. This work will provide a reference for the taste improvement of SGs.

Glycosyltransferases: Mining, engineering and applications in biosynthesis of glycosylated plant natural products

UDP-Glycosyltransferases (UGTs) catalyze the transfer of nucleotide-activated sugars to specific acceptors, among which the GT1 family enzymes are well-known for their function in biosynthesis of natural product glycosides. Elucidating GT function represents necessary step in metabolic engineering of aglycone glycosylation to produce drug leads, cosmetics, nutrients and sweeteners. In this review, we systematically summarize the phylogenetic distribution and catalytic diversity of plant GTs. We also discuss recent progress in the identification of novel GT candidates for synthesis of plant natural products (PNPs) using multi-omics technology and deep learning predicted models. We also highlight recent advances in rational design and directed evolution engineering strategies for new or improved GT functions. Finally, we cover recent breakthroughs in the application of GTs for microbial biosynthesis of some representative glycosylated PNPs, including flavonoid glycosides (fisetin 3-O-glycosides, astragalin, scutellarein 7-O-glucoside), terpenoid glycosides (rebaudioside A, ginsenosides) and polyketide glycosides (salidroside, polydatin).

Two Auxinic Herbicides Affect Brassica napus Plant Hormone Levels and Induce Molecular Changes in Transcription

With the introduction of the new auxinic herbicide halauxifen-methyl into the oilseed rape (Brassica napus) market, there is a need to understand how this new molecule interacts with indigenous plant hormones (e.g., IAA) in terms of crop response. The aim of this study was to investigate the molecular background by using different growth conditions under which three different auxinic herbicides were administered. These were halauxifen-methyl (Hal), alone and together with aminopyralid (AP) as well as picloram (Pic). Three different hormone classes were determined, free and conjugated indole-3-acetic acid (IAA), aminocyclopropane carboxylic acid (ACC) as a precursor for ethylene, and abscisic acid (ABA) at two different temperatures and growth stages as well as over time (2–168 h after treatment). At 15 °C growth temperature, the effect was more pronounced than at 9 °C, and generally, the younger leaves independent of the developmental stage showed a larger effect on the alterations of hormones. IAA and ACC showed reproducible alterations after auxinic herbicide treatments over time, while ABA did not. Finally, a transcriptome analysis after treatment with two auxinic herbicides, Hal and Pic, showed different expression patterns. Hal treatment leads to the upregulation of auxin and hormone responses at 48 h and 96 h. Pic treatment induced the hormone/auxin response already after 2 h, and this continued for the other time points. The more detailed analysis of the auxin response in the datasets indicate a role for GH3 genes and genes encoding auxin efflux proteins. The upregulation of the GH3 genes correlates with the increase in conjugated IAA at the same time points and treatments. Also, genes for were found that confirm the upregulation of the ethylene pathway.

Recent advances in activity-based probes (ABPs) and affinity-based probes (AfBPs) for profiling of enzymes

Activity-based protein profiling (ABPP) is a technique that uses highly selective active-site targeted chemical probes to label and monitor the state of proteins. ABPP integrates the strengths of both chemical and biological disciplines. By utilizing chemically synthesized or modified bioactive molecules, ABPP is able to reveal complex physiological and pathological enzyme-substrate interactions at molecular and cellular levels. It is also able to provide critical information of the catalytic activity changes of enzymes, annotate new functions of enzymes, discover new substrates of enzymes, and allow real-time monitoring of the cellular location of enzymes. Based on the mechanism of probe-enzyme interaction, two types of probes that have been used in ABPP are activity-based probes (ABPs) and affinity-based probes (AfBPs). This review highlights the recent advances in the use of ABPs and AfBPs, and summarizes their design strategies (based on inhibitors and substrates) and detection approaches.

Selective profiling of steviol-catalyzing UDP-glycosyltransferases with a metabolically synthesized probe

Selective profiling of steviol-catalyzing UDP-glycosyltransferases in plants was accomplished with a probe metabolically synthesized from two substrate-derived components comprising an alkynylated sugar receptor (steviol) module and a diazirine-modified sugar donor (UDP-glucose) module, thereby illustrating a facile approach for harnessing biosynthetic enzymes of natural glycosides in plants for synthetic biology.

Chemoproteomic Profiling of Cobalamin-Independent Methionine Synthases in Plants with a Covalent Probe

Cobalamin-independent methionine synthases (MS) are zinc-binding methyltransferases that catalyze de novo methionine biosynthesis in higher plants, which are enzymes critically involved in seed germination and plant growth. Here, we report a highly selective sulfonyl fluoride-based probe for chemoproteomic profiling of MS enzymes in living systems of the model plant Arabidopsis thaliana, as implemented in in-gel-, mass spectrometry-, and imaging-based platforms. This probe holds promise for facilitating and accelerating fundamental research and industrial application of MS enzymes, particularly in the contexts of MS1/2-targeting herbicide screening and design.

Research advances in cytochrome P450-catalysed pharmaceutical terpenoid biosynthesis in plants

Terpenoids, the biggest class of plant secondary metabolites, have a wide range of significant physiological roles, while many of them are important natural drugs. Biosynthesis of pharmaceutical terpenoids in plants is a fairly complex process, most of which involves cytochrome P450 (CYP450) monooxygenases. CYP450 enzymes are versatile biocatalysts that play critical roles in terpenoid skeleton modification and structural diversity. Therefore, the discovery and identification of CYP450 genes is significant for elucidating the terpenoid biosynthetic pathway. This review summarizes the progress and cloning strategies relating to CYP450s in pharmaceutical terpenoid biosynthesis of the past decade.