Cathepsin D from pig myometrium. Characterization of the proteinase.
The purification of cathepsin D from pig uterus by two-step affinity chromatography on concanavalin A- and pepstatin-Sepharose was described previously [Afting & Becker (1981) Biochem. J. 197, 519-522]. In this paper, chemical and physical properties of the proteinase are presented. The purified enzyme showed three bands on SDS (sodium dodecyl sulphate)/polyacrylamide-gel electrophoresis, one main band corresponding to an Mr of 31 000 and two minor bands with Mr values of 43 000 and 15 000 respectively. Gel filtration on Bio-gel P-150 and sedimentation-diffusion equilibrium studies give an Mr for the main band of about 35 000. The pI of the enzyme was determined to be 7.2. Haemoglobin was the best substrate, with a Km value of 6.4 X 10(-6)M. It was hydrolysed with a pH optimum between 3.0 and 3.3 for a substrate concentration of 100 microM. The proteinase was stable over the pH range of 3.5-6.5. At pH 6 the enzyme showed stability up to a temperature of 50 degrees C; at pH 3 the activity was already decreased below 40 degrees C. Carbohydrate studies resulted in the staining of all three bands on an SDS/polyacrylamide gel by thymol/H2SO4. After treatment with endo-beta-N-acetylglucosaminidase H, all three bands were shifted to a region of lower Mr. Of various inhibitors tested, only pepstatin was strongly inhibiting, with a Ki of 2.1 X 10(-9)M.
D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D002402:Cathepsin D; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008970:Molecular Weight; D009215:Myometrium / Q000201:enzymology*; D010436:Pepstatins / Q000494:pharmacology; D013379:Substrate Specificity; D013552:Swine; D013696:Temperature
D002241:Carbohydrates; D010436:Pepstatins; C014195:Streptomyces pepsin inhibitor; D002403:Cathepsins; D002402:Cathepsin D; C031375:pepstatin