[Function of flavoprotein monooxygenases in natural product biosynthesis]

Flavoprotein monooxygenases(FPMOs) and cytochrome P450(CYP450) oxygenases are pivotal monooxygenases in nature, catalyzing crucial redox reactions in diverse biological processes and contributing to the synthesis of highly complex natural products. While CYP450 enzymes have been extensively reported and studied, numerous FPMOs have also been discovered in past research endeavors, yet their classification, catalytic reactions, and catalytic mechanisms remain to be systematically analyzed. This paper comprehensively reviews the latest advancements in FPMOs research, initiating with a classification based on sequence similarities and distinct structural features. It delves into the catalytic characteristics of three subfamilies(FMO, BVMO, and NMO) within Class B FPMOs of plants, which are integral to biosynthetic pathways of natural products. Class B FPMOs encompass two canonical Rossmann fold motifs(FAD-binding GxGxxG and NADPH-binding GxGxxA), along with a central FMO recognition motif FxGxxxHxxxF/Y/W. These enzymes play a key role in regulating various metabolic routes and precisely modulate plant growth and development. Furthermore, the review summarizes the applications of Class B FPMOs of plants, showcasing through concrete examples their potential in synthesizing natural products such as auxins, indigo, and cyanogenic glycosides. These insights will broaden and deepen our understanding of FPMOs, fostering their transition from fundamental research to practical applications. More optimized biosynthetic pathways can be devised by leveraging FPMOs, conducive to the development of novel strategies and tools for agriculture, plant protection, natural product biosynthesis, and synthetic biology.