Lysosomal acid proteinase of rabbit liver.
1. Acid proteinase from rabbit liver lysosomes was purified about 1000-fold, on a protein basis. 2. The purification procedure involved isolation of a lysosomal-mitochondrial pellet and conversion of this into an acetone-dried powder. 3. The enzyme was extracted with an acidic buffer and subjected to column chromatography with DEAE-Sephadex and Sephadex G-100. 4. The molecular weight of the enzyme was 50000-52000. 5. Maximal activity against haemoglobin was obtained at pH3.2; serum albumin was attacked, but very much more slowly. 6. Several possible inhibitors of the enzyme were tested. Thiol-blocking reagents, several inhibitors of trypsin and chymotrypsin, and a chelating agent were without effect. 7. The enzyme was competitively inhibited by 3-phenylpyruvic acid at low concentrations. 8. Dithiothreitol caused rapid inactivation of the enzyme at pH8. 9. It is concluded that this enzyme is a form of cathepsin D, which may be widely distributed in lysosomes.
D000818:Animals; D002403:Cathepsins / Q000032:analysis* / Q000037:antagonists & inhibitors; D002845:Chromatography; D004586:Electrophoresis; D006454:Hemoglobins / Q000037:antagonists & inhibitors; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000166:cytology; D008247:Lysosomes / Q000201:enzymology*; D008928:Mitochondria / Q000032:analysis; D008970:Molecular Weight; D011817:Rabbits; D012710:Serum Albumin, Bovine / Q000037:antagonists & inhibitors
D006454:Hemoglobins; D012710:Serum Albumin, Bovine; D002403:Cathepsins