Diterpene Synthases as Gatekeepers of Bioactive Diterpenoids: A Resource for Discovery and Engineering toward Efficient Synthesis

Diterpenoids represent a large and structurally diverse class of natural products, some of which are widely used in the medicine, agriculture, cosmetics, and food industries. However, the application of most diterpenoids faces challenges, such as complex sources, low yields, and insufficient purity. Using synthetic biology and metabolic engineering to construct microbial cell factories for diterpenoid production is an emerging strategy that overcomes the limitations of plant extraction and chemical synthesis. Diterpene synthases (diTPSs) serve as gatekeepers and rate-limiting enzymes in diterpenoid biosynthesis, representing a key bottleneck for large-scale production. In this Review, we summarize the biological activities and practical applications of representative diterpenoids according to their chemical structures. Then, we compile 562 functionally characterized diTPSs from previous studies to establish a comprehensive functional database. Through integrated bioinformatic analyses, we elucidate the catalytic mechanisms, product diversity, and phylogenetic distribution of the different functional diTPS classes. Finally, we discuss future directions for the development of diTPSs as core functional elements in synthetic biology, providing a foundation for ongoing research in this field.