New Glycosyltransferases in Panax notoginseng Perfect Main Ginsenosides Biosynthetic Pathways

Panax notoginseng: panoramagram of phytochemical and pharmacological properties, biosynthesis, and regulation and production of ginsenosides

Panax notoginseng is a famous perennial herb widely used as material for medicine and health-care food. Due to its various therapeutic effects, research work on P. notoginseng has rapidly increased in recent years, urging a comprehensive review of research progress on this important medicinal plant. Here, we summarize the latest studies on the representative bioactive constituents of P. notoginseng and their multiple pharmacological effects, like cardiovascular protection, anti-tumor, and immunomodulatory activities. More importantly, we emphasize the biosynthesis and regulation of ginsenosides, which are the main bioactive ingredients of P. notoginseng. Key enzymes and transcription factors (TFs) involved in the biosynthesis of ginsenosides are reviewed, including diverse CYP450s, UGTs, bHLH, and ERF TFs. We also construct a transcriptional regulatory network based on multi-omics data and predicted candidate TFs mediating the biosynthesis of ginsenosides. Finally, the current three major biotechnological approaches for ginsenoside production are highlighted. This review covers advances in the past decades, providing insights into quality evaluation and perspectives for the rational utilization and development of P. notoginseng resources. Modern omics technologies facilitate the exploration of the molecular mechanisms of ginsenoside biosynthesis, which is crucial to the breeding of novel P. notoginseng varieties. The identification of functional enzymes for biosynthesizing ginsenosides will lead to the formulation of potential strategies for the efficient and large-scale production of specific ginsenosides.

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.

Enhancing the thermostability and activity of glycosyltransferase UGT76G1 via computational design

The diterpene glycosyltransferase UGT76G1, derived from Stevia rebaudiana, plays a pivotal role in the biosynthesis of rebaudioside A, a natural sugar substitute. Nevertheless, its potential for industrial application is limited by certain enzymatic characteristics, notably thermostability. To enhance the thermostability and enzymatic activity, we employed a computational design strategy, merging stabilizing mutation scanning with a Rosetta-based protein design protocol. Compared to UGT76G1, the designed variant 76_4 exhibited a 9 °C increase in apparent Tm, a 2.55-fold increase rebaudioside A production capacity, and a substantial 11% reduction in the undesirable byproduct rebaudioside I. Variant 76_7 also showed a 1.91-fold enhancement rebaudioside A production capacity, which was maintained up to 55 °C, while the wild-type lost most of its activity. These results underscore the efficacy of structure-based design in introducing multiple mutations simultaneously, which significantly improves the enzymatic properties of UGT76G1. This strategy provides a method for the development of efficient, thermostable enzymes for industrial applications.