Proteolytic Activation of Human Procathepsin D

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Abstract
The occurrence of multiple proteolytic processing steps is typical of lysosomal enzyme biosynthesis, but not characteristic of the other aspartyl proteases. Cathepsin D, a lysosomal aspartyl protease, is proteolytically processed several times during biosynthesis. A summary of these processing steps is shown in Figure 1. Although the activity and structure of cathepsin D has been studied in great detail1,2,3,4 and the activation of procathepsin D is known to be dependent upon this proteolytic processing, the proteases and the exact cleavage sites which the proteases use to accomplish the processing of cathepsin D are, for the most part, unknown. The activation of the aspartyl protease proenzymes pepsinogen and prorenin has been explored in depth.4,5 In this article we have summarized our recent studies on the proteolytic activation of human procathepsin D.