CTSD and Huntington disease: Moreover, it modulates the activity of diverse polypeptides, enzymes, and growth factors, and is thereby an essential regulator of cell signaling [28], while cathepsin D imbalance might play an important role in acute kidney injury [29], Huntington’s disease [30], Parkinson’s disease [31], Alzheimer’s disease [32], pancreatitis [33] and coronary events [34,35], making cathepsin D a vital protease for maintaining cellular homeostasis.