PSMA1 is a prosomal protein who takes part in a nonlysosomal ATP/ubiquitin-dependent proteolytic pathway. PSMA1 is a multicatalytic proteinase complex that is characterized by its capacity to cleave peptides with Arg, Phe, Tyr, Leu, and Glu next to the leaving group at neutral or slightly basic pH. PSMA1 is vastly expressed in prostate epithelium.