PSMA1 is a prosomal protein involved in a nonlysosomal ATP/ubiquitin-dependent proteolytic pathway. The protein is a multicatalytic proteinase complex which is characterized by its ability to cleave peptides with Arg, Phe, Tyr, Leu, and Glu adjacent to the leaving group at neutral or slightly basic pH. This protein highly expressed in prostate epithelium. Recombinant human PSMA1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.