The MEROPS database as a protease information system

Peptidases (often termed proteases) are of great relevance to biology, medi cine, and biotechnology. This practical importance creates a need for an in tegrated source of information about peptidases. In the MEROPS database (ww w.merops.ac.uk), peptidases are classified by structural similarities in th e parts of the molecules responsible for their enzymatic activity. They are grouped into families on the basis of amino acid sequence homology, and th e families are assembled into clans in light of evidence that they share co mmon ancestry. The evidence for clan-level relationships usually comes from similarities in tertiary structure, but we suggest that secondary structur e profiles may also be useful in the future. The classification forms a fra mework around which a wealth of supplementary information about the peptida ses is organized. This includes images of three-dimensional structures, ali gnments of matching human and mouse ESTs, comments on biomedical relevance, human and other gene symbols, and literature references linked to PubMed. For each family, there is an amino acid sequence alignment and a dendrogram . There is a list of all peptidases known from each of over 1000 species, t ogether with summary data for the distributions of the families and clans t hroughout the major groups of organisms. A set of online searches provides access to information about the location of peptidases on human chromosomes and peptidase substrate specificity. (C) 2001 Academic Press.