The two sides of enzyme-substrate specificity: lessons from the aspartic proteinases

Like most proteolytic enzymes, the aspartic proteinases bind substrates and most inhibitors within an extended active site cleft. Bound ligands typica lly adopt a P-strand conformation. Interactions with groups on both sides o f the cleft determine the primary as well as secondary specificity of the e nzymes. We have pursued the discovery of the sometimes subtle distinctions between members of the aspartic proteinase family by two routes. In the fir st case, we have constructed sets of oligopeptide substrates with systemati c variation in each position to assess interactions at one position at a ti me. In the second type of experiment, we have altered residues of the enzym es in order to test theories of selectivity. The combination of the two app roaches has provided a better understanding of the forces involved in deter mining specificity of enzyme action. (C) 2000 Elsevier Science B.V. All rig hts reserved.