Schematic description of CSA database. The blue block demonstrates the ‘original’ enzyme data for enolase, PDB code 5enl. The central block shows ‘homologous’ enzymes identified by PSI-BLAST analysis, and one of these, PDB code 1pdz, is highlighted in green as an example homologue. The green block at the bottom demonstrates the ‘homologous’ enzyme datzyme data set, in Venn diagram form. The number of residues annotated by each database is given, along with the number of identical residues found in both databases.