Plant Prenylflavonoids and Prenyltransferases Related to their Biosynthesis

As the most widely distributed phenolic compounds in the plant kingdom, flavonoids play an integral role in plant reproduction and defense. Also, they represent many important quality traits of edible plants like color and antioxidants, and have a variety of biological activities beneficial to human health. To diversify the functions of synthesized flavonoids, plants have evolved various enzymes to perform structural modifications on different flavonoid backbones. One of these modifications is prenylation, which refers to the attachment of an isoprenoid moiety, most commonly a prenyl (C5) group. Numerous structure-activity analyses of prenylflavonoids have shown that isopentenyl substitutions at specific sites can significantly expand and enhance their chemical properties, bioactivities and potential health benefits. This review summarizes prenylflavonoids reported so far in all plant species and highlights the current knowledge on naturally occurring prenyltransferases from different biological sources that can act on plant flavonoids to synthesize prenylflavonoids. Most of them have strict flavonoid substrate- and regio-specificities, and they provide a valuable gene repository to facilitate the efficient scale-up production of flavonoids with specific prenylation patterns in cell factories. To truly achieve this goal, it is necessary to explore more diversified natural prenyltransferases, and to optimize the bioreactors system such as pathway regulation and modular co-culture engineering in the future.