The article discusses the development and application of flavin-dependent "ene"-reductases (EREDs) as catalysts for generating and controlling radical intermediates in chemical synthesis. EREDs are enzymes that can facilitate the asymmetric reduction of electronically activated alkenes, and the authors have explored their potential for catalyzing a variety of radical-mediated reactions. The study focuses on two main approaches for radical initiation: ground-state electron transfer and photoexcitation. Ground-state electron transfer involves using the flavin mononucleotide hydroquinone (FMN_hq) as an electron donor, while photoexcitation involves exciting FMN_hq with light to generate a more reducing singlet excited state. The authors detail the mechanisms and applications of these approaches, including asymmetric radical cyclizations, intermolecular radical reactions, and the synthesis of various functional groups. They also highlight the potential for using other cofactor-dependent proteins to explore new types of enzyme-catalyzed radical reactions. The work demonstrates the versatility and selectivity of EREDs in chemical synthesis, providing a valuable tool for asymmetric synthesis and chemical engineering.The article discusses the development and application of flavin-dependent "ene"-reductases (EREDs) as catalysts for generating and controlling radical intermediates in chemical synthesis. EREDs are enzymes that can facilitate the asymmetric reduction of electronically activated alkenes, and the authors have explored their potential for catalyzing a variety of radical-mediated reactions. The study focuses on two main approaches for radical initiation: ground-state electron transfer and photoexcitation. Ground-state electron transfer involves using the flavin mononucleotide hydroquinone (FMN_hq) as an electron donor, while photoexcitation involves exciting FMN_hq with light to generate a more reducing singlet excited state. The authors detail the mechanisms and applications of these approaches, including asymmetric radical cyclizations, intermolecular radical reactions, and the synthesis of various functional groups. They also highlight the potential for using other cofactor-dependent proteins to explore new types of enzyme-catalyzed radical reactions. The work demonstrates the versatility and selectivity of EREDs in chemical synthesis, providing a valuable tool for asymmetric synthesis and chemical engineering.