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Identification of a precursor form of cathepsin D in microsomal lumen: Characterization of enzymatic activation and proteolytic processingin vitro

Authors
Journal
Biochemical and Biophysical Research Communications
0006-291X
Publisher
Elsevier
Publication Date
Volume
148
Issue
1
Identifiers
DOI: 10.1016/0006-291x(87)91115-6

Abstract

Abstract A precursor form of cathepsin D with 45 kDa was demonstrated in the rat liver microsomal lumen by immunoblotting analysis. The microsomal fraction containing procathepsin D which passed through a pepstatin-Sepharose resin showed no appreciable activity of cathepsin D. The in vitro incubation of this fraction at pH 3.0 resulted in a gradual increase of proteolytic activity toward hemoglobin as substrate and also, the proteolytic conversion of procathepsin D to the mature form was concomitantly observed. The proteolytic processing step was sensitive to pepstatin. These results suggest that procathepsin D is inactive in the endoplasmic reticulum and may be converted to the active forms by autoproteolytic processing mechanism at acidic pH during biosynthesis.

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