[Intracellular protein breakdown. VI. Isolation, properties and biological significance of cathepsin D from rat liver].
The preparation and properties of cathepsin D from rat liver are reported. The enzyme is an endopeptidase of lysosomal origin. The molecular weight was estimated to be 49000 by sodium-dodecylsulfate electrophoresis. We did not find any dissociation into subunits under reducing conditions, in contrast to some other authors. We found the enzyme to occur in at least 4 forms with the isoelectric points 5.87, 5.65, 5.41 and 5.13. Strong -SH-blocking reagents inhibit the activity, but the most powerful and specific inhibitor was pepstatin (Ki=38 nM). The substrate specificity is discussed. There was no proof for any zymogen activation in a great number of experiments. Since the cathepsins B1, B3 and L obviously seem to play the major role in the intracellular protein breakdown within the rat liver, the main task of cathepsin D is the degradation of extracellular proteins in this organ.
D000818:Animals; D002403:Cathepsins / Q000302:isolation & purification / Q000378:metabolism*; D002729:Chloromercuribenzoates / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D005779:Immunodiffusion; D007122:Immunoelectrophoresis; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008628:Mercury / Q000494:pharmacology; D010436:Pepstatins / Q000494:pharmacology; D051381:Rats
D002729:Chloromercuribenzoates; D010436:Pepstatins; D003300:Copper; D002403:Cathepsins; D008628:Mercury
Intrazellulärer Proteinabbau. VI. Isolierung, Eligenschaften und biologische Bedeutung von Kathepsin D aus der Rattenleber