Cathepsin D is an aspartic endo-protease which is found to be distributed ubiquitously in lysosomes, in humans it is encoded by the CTSD gene. The main functions of this protein include degrading proteins and activating precursors of bioactive proteins within pre-lysosomal compartments. This proteinase is a family member of the peptidase A1, it displays specificity which is very similar to but also narrower than that of pepsin A. 

ELISA kit information:

• Reactivity: Human
• Sample Type: Biological Fluids, Tissue Homogenates, Plasma, Serum
• Sensitivity: 28.125 pg/ml
• Target: Cathepsin D, CTSD