SDR: Structure, mechanism of action, and substrate recognition

Short-chain dehydrogenases/reductases (SDR) constitute a large protein family. The SDR family now includes more than 1,000 enzymes from humans, mammals, insects and bacteria, and exhibits a wide variety of substrate specificity for steroids, retinoids, prostaglandins, sugars, alcohols and other small molecules. These enzymes have a residue identity level of 15-30 %. Much has been done in the last decade to understand the structure-function relationships in the SDR enzymes. This review summarizes recent progress of structural and functional studies of the enzymes belonging to the SDR family (X-ray crystal structure analyses and site-directed mutagenesis studies). Based on these studies, the three-dimensional structure, catalytic mechanism, coenzyme specificity, and substrate specificity of the SDR enzymes are discussed.