Mammalian proprotein convertases (PCs) are a group of endoproteases that process a variety of molecules, including growth factors, hormones, serum proteins, bacterial toxins, and viral envelope glycoproteins. Biochemical and cellular studies have provided valuable insights into the functions of these proteases. Although both PC6B and furin are expressed throughout the body and share nearly identical enzymatic characteristics, my research presented in this thesis demonstrates that these two proteases are concentrated in distinct subcellular compartments.