The International Protein Index (IPI)[1] is database that was created to give the proteomics community a resource that enables
IPI was launched in 2001 by the European Bioinformatics Institute (EBI) when databases cataloguing human genes varied greatly and had few links between them. Since then much more data has been produced giving a more complete picture and databases have collaborated to synchronize data. Currently many model organisms have a reference set of genes/proteins which are catalogued in Ensembl/UniProt respectively, as well as other species specific databases.
Due to advances in data organization the need for IPI is diminishing. The EBI has announced that this service will be closing when appropriate and has advised users of its services to employ UniProtKB accession numbers as their protein identifiers.