Identification of a precursor form of cathepsin D in microsomal lumen: characterization of enzymatic activation and proteolytic.
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.
Nishimura
Y
Y
Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Higaki
M
M
Kato
K
K
D000818:Animals; D002402:Cathepsin D / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D004789:Enzyme Activation; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D011499:Protein Processing, Post-Translational; D051381:Rats; D011919:Rats, Inbred Strains
D002402:Cathepsin D