Abstract
PROCESSING of propeptides involves the cleavage of one or more peptide bonds in the inactive precursor resulting in a smaller , sometimes fragmented, active protein . Very often these processing enzymes are unique to a particular propeptide and possess unusual specificity
aimed at a limited number of cleavage l sites. A paper on page 768 of this issue and one earlier this month in Science2, describe such a protease whose function is the processing of the propeptide from which the cytokine interleukin-l~ (IL- l~) is derived. This specific proteolytic activation is part of a control mechanism designed to prevent random or un-wanted side reactions, which might damage the cell by the activation of potentially dangerous molecules. Consequently , each activation process is highly specific for its own particular target.