Reconstructing the evolutionary history of F₄₂₀-dependent dehydrogenases

During the last decade the number of characterized F₄₂₀-dependent enzymes has significantly increased. Many of these deazaflavoproteins share a TIM-barrel fold and are structurally related to FMN-dependent luciferases and monooxygenases. In this work, we traced the origin and evolutionary history of the F₄₂₀-dependent enzymes within the luciferase-like superfamily. By a thorough phylogenetic analysis we inferred that the F₄₂₀-dependent enzymes emerged from a FMN-dependent common ancestor. Furthermore, the data show that during evolution, the family of deazaflavoproteins split into two well-defined groups of enzymes: the F₄₂₀-dependent dehydrogenases and the F₄₂₀-dependent reductases. By such event, the dehydrogenases specialized in generating the reduced deazaflavin cofactor, while the reductases employ the reduced F₄₂₀ for catalysis. Particularly, we focused on investigating the dehydrogenase subfamily and demonstrated that this group diversified into three types of dehydrogenases: the already known F₄₂₀-dependent glucose-6-phosphate dehydrogenases, the F₄₂₀-dependent alcohol dehydrogenases, and the sugar-6-phosphate dehydrogenases that were identified in this study. By reconstructing and experimentally characterizing ancestral and extant representatives of F₄₂₀-dependent dehydrogenases, their biochemical properties were investigated and compared. We propose an evolutionary path for the emergence and diversification of the TIM-barrel fold F₄₂₀-dependent dehydrogenases subfamily.