Regulatory Factors and Motifs in SDR Enzymes

At present, well over 700 different enzymes are grouped into the superfamily of short-chain dehydrogenases/reductases (SDR), comprising isomerases, lyases and oxidoreductases, thereby constituting one of the largest protein superfamilies known to date (Jornvall et al., 1995; Persson et al., this volume). Sequence comparisons between the different SDR members reveal typically ~ 25 % residue identity, with some highly conserved sequenmotifs in common. The general architecture of this protein family has been greatly furthered by crystallographic analysis of some 10 distinct enzymes, revealing a close identical pattern of α/β folding, a common nucleotide binding site and a Tyr-dependent acid-base catalytic mechanism. In many cases, these crystallographic data allow the coter-aided molecular modelling of three-dimensional structures of still further members, thereby opening the possibility of predicting or exploring substrate specificities of proteins with unknown function.