Cathepsin D of rabbit skin: An immunoenzymic study

Cathepsin D, one of the major lysosomal proteinases, has been identified in rabbit skin. A line of complete immunologic identity between crude skin extracts and pure rabbit liver cathepsin D was found in immunodiffusion studies using sheep antirabbit cathepsin D antiserum. The addition of sheep antiserum against rabbit cathepsin D to skin extracts resulted in the precipitation of 85% of the hemoglobin degrading activity measured at pH 3.2. Selective removal of the enzyme from the skin extracts by precipitation with antibody revealed that cathepsin D was responsible for degradation of skin protein at acid pH. Cathepsin D may play a major role in both extracellular and intracellular catabolism in skin.