Enables aspartic-type endopeptidase activity. Acts upstream of or within autophagosome assembly. Located in extracellular space and lysosome. Is expressed in several structures, including central nervous system; extraembryonic component; eye; genitourinary system; and optic nerve. Used to study neuronal ceroid lipofuscinosis 10. Human ortholog(s) of this gene implicated in Alzheimer's disease; breast cancer; and neuronal ceroid lipofuscinosis 10. Orthologous to human CTSD (cathepsin D). [provided by Alliance of Genome Resources, Apr 2022]