“…Cathepsin D has been cloned and sequenced in a number of mammalian species [9,10], and in several species of fish such as tilapia (Tilapia nilotica  Tilapia aurea) [11], rainbow trout (Oncorhynchus mykiss) [12], Antarctic icefish (Chionodraco hamatus) [13], seabream (Sparus aurata) [14], zebrafish (Danio rerio) [15], carp (Cyprinus carpio) [16], herring (Clupea harengus) [17], pufferfish (Takifugu rubripes) [18], Atlantic cod (Gadus morhua) [19], and turbot (Scophthalmus maximus) [20]. In most fish species, cathepsin D was found to be mainly expressed in the spleen and liver [19], but it is also abundant in skin mucosa [21] and muscle based on protein levels [11,17,22].…”