The α,β-Double Bond Reductases (DBRs): An Overview

Scientific investigations have increasingly focused on enzymatic mechanisms that scavenge reactive carbonyl species (RCS) in plants, motivated by the cytotoxic effects of these compounds, which can induce oxidative damage and even trigger programmed cell death. The α,β-double bond reductase (DBR) that specifically reduces the C=C double bond of α,β-unsaturated aldehydes/ketones belongs to the medium-chain dehydrogenase/reductase superfamily (MDRs). DBRs from different plants possess two identical domains: a nucleotide-binding domain with a shared, conserved GXXS and A(G)XXGXXG motif, along with a substrate-binding domain with active site residues. In vitro, DBRs catalyze the reduction of a variety of substrates, including long-chain, short-chain, cyclic aliphatic compounds, as well as phenylpropanoid and phenylbutane aromatic compounds. DBRs are extensively involved in the metabolic detoxification of RCS, which primarily improve stress resistance of the plants. DBRs have also been found to participate in the biosynthesis of several active compounds which exert unique defensive functions and pharmacological activities. In the realm of industrial synthetics, DBRs stand out as promising catalysts, capable of delivering a reduced chiral product with exceptional yield and chemical purity. Phylogenetic analysis and the catalytic mechanism of DBRs are now poised to be interrogated using modern genomic and bioinformatic approaches.