Structural Differences Between Rabbit Cathepsin E and Cathepsin D

: Rabbit cathepsins D and E were isolated from bone marrow. Both enzymes were purified by affinity chromatography on pepstatin-Sepharose 4B and Con A-Sepharose 4B. Purity of the enzymes was ascertained by two-dimensional gel electrophoresis after iodination. The isoelectric point of cathepsin D was found to be 6.95. Cathepsin E was shown to consist of two subunits having molecular masses each of 40 kDa and isoelectric points of 4.60 and 4.65, respectively. The amino-acid composition of cathepsin E was found to be different from that of cathepsin D.