BACE2 and Alzheimer disease: Peptidases within this subfamily include: pepsin A (EC 3.4.23.1), gastricsin (EC 3.4.23.3) and chymosin (EC 3.4.23.4), which are digestive enzymes in the stomach; cathepsin D (EC 3.4.23.5), which is a lysosomal enzyme that degrades phagocytozed peptides and proteins; renin (EC 3.4.23.15), which is a peptidase that processes angiotensinogen; and memapsins 1 (or BACE-2, EC 3.4.23.45) and 2 (BACE-1, EC 3.4.23.46), widely distributed peptidases of unknown function but which may be involved in Alzheimer's disease (memapsin-2 is currently under investigation as a drug target [4]).