Discovery of unique CYP716C oxidase involved in pentacyclic triterpene biosynthesis from Camptotheca acuminata

The key role of cytochrome P450s in the biosynthesis of plant derived natural products

Cytochrome P450 (CYP450 or CYP450, abbreviated as CYP450) represents a large family of self-oxidizable heme proteins, belonging to the class of monooxygenases, and is named because of the specific absorption peak at 450 nm in its ferrous/CO-bound complex. Cytochrome P450 has a wide spectrum of substrates and a rich variety of catalytic reactions, plays an important role in drug metabolism, natural product biosynthesis, and biocatalysis industry. In the biosynthesis of plant natural products, it plays an important role, especially in the downstream synthesis pathway and structural modification after skeleton synthesis. There are abundant natural products from plants, including terpenes, alkaloids, flavonoids, steroidal saponins, etc., which have great development value in the medical field. In the biosynthetic pathways of these natural products, cytochrome P450 enzymes often play an important role. They can serve as rate-limiting enzymes in the biosynthetic pathways or as modifying enzymes for the structural diversity of compounds. So, a deeper understanding of cytochrome P450 enzymes in the natural product synthesis pathway will enhance the development of natural products and advance the study of their synthetic biology. This review offers an overview of the biosynthesis of key medicinal natural products, with a particular focus on the critical role of cytochrome P450 enzymes in key catalytic steps. It also highlights recent advancements in the research of natural product biosynthesis and synthetic biology.

Recent trends in the elucidation of complex triterpene biosynthetic pathways in horticultural trees

Triterpene (C30 isoprene compounds) represents the most structurally diverse class of natural products and has been extensively exploited in the food, medicine, and industrial sectors. Decades of research on medicinal triterpene biosynthetic pathways have revealed their roles in stress tolerance and shaping microbiota. However, the biological function and mechanism of triterpenes are not fully identified. Even this scientific window narrows down for horticultural trees. The lack of knowledge and a scalable production system limits the discovery of triterpene pathways. Recent synthetic biology research revealed several important biosynthetic pathways that define their roles and address many societal sustainability challenges. Here, I review the chemical diversity and biosynthetic enzymes involved in triterpene biosynthesis of horticultural trees. This review also outlines the integrated Design-Build-Test-Learn (DBTL) pipelines for the discovery, characterization, and optimization of triterpene biosynthetic pathways. Further, these DBTL components share many fundamental and technical difficulties, highlighting opportunities for interdisciplinary collaboration between researchers worldwide. This advancement opens up unprecedented opportunities for the bioengineering of triterpene compounds toward development and scaleup processes.

Discovery of a novel flavonol O-methyltransferase possessing sequential 4'- and 7-O-methyltransferase activity from Camptotheca acuminata Decne

The biosynthetic route for flavonol in Camptotheca acuminata has been recently elucidated from a chemical point of view. However, the genes involved in flavonol methylation remain unclear. It is a critical step for fully uncovering the flavonol metabolism in this ancient plant. In this study, the multi-omics resource of this plant was utilized to perform flavonol O-methyltransferase-oriented mining and screening. Two genes, CaFOMT1 and CaFOMT2 are identified, and their recombinant CaFOMT proteins are purified to homogeneity. CaFOMT1 exhibits strict substrate and catalytic position specificity for quercetin, and selectively methylates only the 4'-OH group. CaFOMT2 possesses sequential O-methyltransferase activity for the 4'-OH and 7-OH of quercetin. These CaFOMT genes are enriched in the leaf and root tissues. The catalytic dyad and critical substrate-binding sites of the CaFOMTs are determined by molecular docking and further verified through site-mutation experiments. PHE181 and MET185 are designated as the critical sites for flavonol substrate selectivity. Genomic environment analysis indicates that CaFOMTs evolved independently and that their ancestral genes are different from that of the known Ca10OMT. This study provides molecular insights into the substrate-binding pockets of two new CaFOMTs responsible for flavonol metabolism in C. acuminata.