Radical Control in Binuclear Copper Enzymes: Structure, Dioxygen Activation, and Mechanisms

Copper-dependent enzymes catalyze a wide range of selective oxidative transformations through activation of dioxygen, with radical chemistry frequently serving as a key strategy for the activation of inert chemical bonds. This review focuses on radical-mediated dioxygen activation in representative copper enzymes containing binuclear copper active sites. Particular emphasis is placed on radical-dependent systems such as peptide α-hydroxylating monooxygenase, dopamine β-hydroxylase, and tyramine β-monooxygenase; enzymes for which radical pathways are proposed but not fully established, including BURP-domain peptide cyclases and fungal DUF3328 copper enzymes; and type-III copper proteins (tyrosinases, catechol oxidases and NspF), where transient radical species may arise during catalysis. We also discuss particulate methane monooxygenase, whose catalytic metal center has undergone continuous reinterpretation. Through comparative analysis, this review highlights the diverse functional roles of radical intermediates in dicopper enzyme catalysis and examines the relationships between active-site structure and dioxygen activation pathways, providing perspectives for future mechanistic investigations.