Despite the importance of protein cleavage, there has been no centralized repository for cleavage data collection and no attempt to curate these cleavages by mapping them to residue positions in protein primary sequence databases. Given that nearly all proteins are eventually degraded, and that any one protein can be degraded by several different peptidases often by cleavages at multiple peptide bonds, the potential total number of cleavages will always exceed the number of known proteins. Up until recently each cleavage had to be characterized biochemically, which meant N-terminal sequencing of the products, a timeconsuming and labour-intensive task. Now that proteomic analyses are possible, where cell lysates or similar samples are subjected to cleavage by a peptidase, peptides isolated, composition determined by mass spectroscopy, and possible source protein(s) determined from the composition (19) , the amount of data is set to rise exponentially. This makes it vitally important that the information be accurately stored and curated. Such a collection made readily available would provide a comprehensive training set for algorithms and software for the prediction of physiological substrates and cleavage positions.