Purification and partial characterization of cathepsin D from porcine (Sus scrofa) liver using affinity chromatography

Cathepsin D, a lysosomal aspartic protease, has been purified from porcine liver using a combination of pepstatin‐A agarose and Affi‐Gel Blue affinity chromatography, followed by size‐exelusion chromatography. The purified protein consists of two polypeptide chains of 15 and 30 kDa, and has an isoelectric point of 6.8. Porcine fiver cathepsin D has maximum activity at pH 2.5‐3.0 as determined by its activity against hemoglobin, with a Kcat of 14.3 s‐1 and a kcat/KM of 2.70×106 s‐1M‐1 as determined by the hydrolysis of a fluorogenic peptide substrate.