Isoaspartyl peptidase/L-asparaginase, also known as ASRGL1, is a 308 amino acid protein belonging to the Ntn-hydrolase family. ASRGL1 has been identified as an autoantigenic protein that is present in the mid-piece of sperm after obstruction of the male reproductive tract. It is expressed highly in testis, but is also expressed in brain, kidney and gastrointestinal tissues. High levels of ASRGL1 have also been identified in ovarian, uterine and mammary tumors in comparison with normal tissues of the same origin. Recombinant human ASRGL1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.